4 (four) is a
number
A number is a mathematical object used to count, measure, and label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with number words. More universally, individual numbers c ...
,
numeral and
digit. It is the
natural number following
3 and preceding
5. It is the smallest
semiprime and
composite number, and is
considered unlucky in many East Asian cultures.
In mathematics
Four is the smallest
composite number, its proper
divisors being and . Four is the sum and product of
two with itself:
+
=
=
x
, the only number
such that
+
=
=
x
, which also makes four the smallest squared
prime number . In
Knuth's up-arrow notation
In mathematics, Knuth's up-arrow notation is a method of notation for very large integers, introduced by Donald Knuth in 1976.
In his 1947 paper, R. L. Goodstein introduced the specific sequence of operations that are now called ''hyperoperati ...
, , and so forth, for any number of up arrows. By consequence, four is the only square one more than a prime number, specifically
three
3 is a number, numeral, and glyph.
3, three, or III may also refer to:
* AD 3, the third year of the AD era
* 3 BC, the third year before the AD era
* March, the third month
Books
* '' Three of Them'' (Russian: ', literally, "three"), a 1901 ...
. The sum of the first four prime numbers
two +
three
3 is a number, numeral, and glyph.
3, three, or III may also refer to:
* AD 3, the third year of the AD era
* 3 BC, the third year before the AD era
* March, the third month
Books
* '' Three of Them'' (Russian: ', literally, "three"), a 1901 ...
+
five +
seven is the only sum of four consecutive prime numbers that yields an
odd prime number,
seventeen, which is the fourth
super-prime. Four lies between the first proper pair of
twin primes,
three
3 is a number, numeral, and glyph.
3, three, or III may also refer to:
* AD 3, the third year of the AD era
* 3 BC, the third year before the AD era
* March, the third month
Books
* '' Three of Them'' (Russian: ', literally, "three"), a 1901 ...
and
five, which are the first two
Fermat prime
In mathematics, a Fermat number, named after Pierre de Fermat, who first studied them, is a positive integer of the form
:F_ = 2^ + 1,
where ''n'' is a non-negative integer. The first few Fermat numbers are:
: 3, 5, 17, 257, 65537, 429496 ...
s, like
seventeen, which is the third. On the other hand, the
square
In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90- degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length a ...
of four 4
2, equivalently the
fourth power
In arithmetic and algebra, the fourth power of a number ''n'' is the result of multiplying four instances of ''n'' together. So:
:''n''4 = ''n'' × ''n'' × ''n'' × ''n''
Fourth powers are also formed by multiplying a number by its cube. Further ...
of two 2
4, is
sixteen; the only number that has
=
as a form of
factorization
In mathematics, factorization (or factorisation, see English spelling differences) or factoring consists of writing a number or another mathematical object as a product of several ''factors'', usually smaller or simpler objects of the same kind ...
. Holistically, there are four elementary arithmetic
operations in mathematics:
addition (+),
subtraction (−),
multiplication (×), and
division
Division or divider may refer to:
Mathematics
*Division (mathematics), the inverse of multiplication
*Division algorithm, a method for computing the result of mathematical division
Military
*Division (military), a formation typically consisting ...
(÷); and four basic
number system
A number is a mathematical object used to count, measure, and label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with number words. More universally, individual numbers can ...
s, the
real numbers
,
rational numbers
,
integers
, and
natural numbers
.
Each natural number divisible by 4 is a difference of squares of two natural numbers, i.e.
=
−
. A number is a multiple of 4 if its last two digits are a multiple of 4. For example, 1092 is a multiple of 4 because .
Lagrange's four-square theorem
Lagrange's four-square theorem, also known as Bachet's conjecture, states that every natural number can be represented as the sum of four integer squares. That is, the squares form an additive basis of order four.
p = a_0^2 + a_1^2 + a_2^2 + a_ ...
states that every positive integer can be written as the sum of at most four
square numbers. Three are not always sufficient; for instance cannot be written as the sum of three squares.
There are four
all-Harshad numbers:
1,
2, ''4'', and
6.
12, which is divisible by four thrice over, is a Harshad number in all bases except
octal.
A four-sided plane figure is a
quadrilateral
In geometry a quadrilateral is a four-sided polygon, having four edges (sides) and four corners (vertices). The word is derived from the Latin words ''quadri'', a variant of four, and ''latus'', meaning "side". It is also called a tetragon, ...
or quadrangle, sometimes also called a ''tetragon''. It can be further classified as a
rectangle or ''oblong'',
kite
A kite is a tethered heavier-than-air or lighter-than-air craft with wing surfaces that react against the air to create lift and drag forces. A kite consists of wings, tethers and anchors. Kites often have a bridle and tail to guide the fac ...
,
rhombus
In plane Euclidean geometry, a rhombus (plural rhombi or rhombuses) is a quadrilateral whose four sides all have the same length. Another name is equilateral quadrilateral, since equilateral means that all of its sides are equal in length. The ...
, and
square
In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90- degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length a ...
.
Four is the highest degree general
polynomial equation
In mathematics, an algebraic equation or polynomial equation is an equation of the form
:P = 0
where ''P'' is a polynomial with coefficients in some field (mathematics), field, often the field of the rational numbers. For many authors, the term '' ...
for which there is a
solution in radicals.
The
four-color theorem
In mathematics, the four color theorem, or the four color map theorem, states that no more than four colors are required to color the regions of any map so that no two adjacent regions have the same color. ''Adjacent'' means that two regions sha ...
states that a
planar graph (or, equivalently, a flat
map
A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes.
Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although ...
of two-dimensional regions such as countries) can be colored using four colors, so that adjacent vertices (or regions) are always different colors. Three colors are not, in general, sufficient to guarantee this. The largest planar
complete graph
In the mathematical field of graph theory, a complete graph is a simple undirected graph in which every pair of distinct vertices is connected by a unique edge. A complete digraph is a directed graph in which every pair of distinct vertices is ...
has four vertices.
A solid figure with four faces as well as four vertices is a
tetrahedron
In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all th ...
, which is the smallest possible number of faces and vertices a
polyhedron can have. The regular tetrahedron, also called a 3-
simplex, is the simplest
Platonic solid. It has four
regular triangle
In geometry, an equilateral triangle is a triangle in which all three sides have the same length. In the familiar Euclidean geometry, an equilateral triangle is also equiangular; that is, all three internal angles are also congruent to each ...
s as faces that are themselves at
dual positions with the vertices of another tetrahedron. Tetrahedra can be inscribed inside all other four Platonic solids, and
tessellate space alongside the
regular octahedron in the
alternated cubic honeycomb.
Four-dimensional space is the highest-dimensional space featuring more than three
regular convex
Convex or convexity may refer to:
Science and technology
* Convex lens, in optics
Mathematics
* Convex set, containing the whole line segment that joins points
** Convex polygon, a polygon which encloses a convex set of points
** Convex polytop ...
figures:
*Two-dimensional: infinitely many
regular polygon
In Euclidean geometry, a regular polygon is a polygon that is direct equiangular (all angles are equal in measure) and equilateral (all sides have the same length). Regular polygons may be either convex, star or skew. In the limit, a sequence ...
s.
*Three-dimensional: five
regular polyhedra
A regular polyhedron is a polyhedron whose symmetry group acts transitively on its flags. A regular polyhedron is highly symmetrical, being all of edge-transitive, vertex-transitive and face-transitive. In classical contexts, many different equival ...
; the five
Platonic solids which are the
tetrahedron
In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all th ...
,
cube,
octahedron
In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at ea ...
,
dodecahedron
In geometry, a dodecahedron (Greek , from ''dōdeka'' "twelve" + ''hédra'' "base", "seat" or "face") or duodecahedron is any polyhedron with twelve flat faces. The most familiar dodecahedron is the regular dodecahedron with regular pentagon ...
, and
icosahedron.
*Four-dimensional: six
regular polychora
In mathematics, a regular 4-polytope is a regular four-dimensional polytope. They are the four-dimensional analogues of the regular polyhedra in three dimensions and the regular polygons in two dimensions.
There are six convex and ten star regu ...
; the
5-cell, 8-cell or
tesseract
In geometry, a tesseract is the four-dimensional analogue of the cube; the tesseract is to the cube as the cube is to the square. Just as the surface of the cube consists of six square faces, the hypersurface of the tesseract consists of e ...
,
16-cell
In geometry, the 16-cell is the regular convex 4-polytope (four-dimensional analogue of a Platonic solid) with Schläfli symbol . It is one of the six regular convex 4-polytopes first described by the Swiss mathematician Ludwig Schläfli in the ...
,
24-cell
In geometry, the 24-cell is the convex regular 4-polytope (four-dimensional analogue of a Platonic solid) with Schläfli symbol . It is also called C24, or the icositetrachoron, octaplex (short for "octahedral complex"), icosatetrahedroid, o ...
,
120-cell, and
600-cell
In geometry, the 600-cell is the convex regular 4-polytope (four-dimensional analogue of a Platonic solid) with Schläfli symbol . It is also known as the C600, hexacosichoron and hexacosihedroid. It is also called a tetraplex (abbreviated from ...
. The
24-cell
In geometry, the 24-cell is the convex regular 4-polytope (four-dimensional analogue of a Platonic solid) with Schläfli symbol . It is also called C24, or the icositetrachoron, octaplex (short for "octahedral complex"), icosatetrahedroid, o ...
, made of regular
octahedra
In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet a ...
, has no analogue in any other dimension; it is
self-dual, with its
24-cell honeycomb dual to the
16-cell honeycomb.
*Five-dimensional and every higher dimension: three regular convex
-
polytope
In elementary geometry, a polytope is a geometric object with flat sides ('' faces''). Polytopes are the generalization of three-dimensional polyhedra to any number of dimensions. Polytopes may exist in any general number of dimensions as an ...
s, all within the infinite family of regular
-
simplexes,
-
hypercubes, and
-
orthoplexes.
The fourth dimension is also the highest dimension where regular
self-intersecting figures exist:
*Two-dimensional: infinitaly many regular
star polygons.
*Three-dimensional: ''four'' regular
star polyhedra, the
regular Kepler-Poinsot star polyhedra.
*Four-dimensional: ten regular
star polychora, the
Schläfli–Hess star polychora. They contain
cells of Kepler-Poinsot polyhedra alongside regular tetrahedra,
icosahedra and
dodecahedra
In geometry, a dodecahedron (Greek , from ''dōdeka'' "twelve" + ''hédra'' "base", "seat" or "face") or duodecahedron is any polyhedron with twelve flat faces. The most familiar dodecahedron is the regular dodecahedron with regular pentagon ...
.
*Five-dimensional and every higher dimension: zero regular
star-polytopes;
uniform star polytopes in dimensions
>
are the most symmetric, which mainly originate from
stellations of regular
-polytopes.
Altogether,
sixteen (or 16 = 4
2) regular convex and star polychora are generated from symmetries of ''four'' (4)
Coxeter
Harold Scott MacDonald "Donald" Coxeter, (9 February 1907 – 31 March 2003) was a British and later also Canadian geometer. He is regarded as one of the greatest geometers of the 20th century.
Biography
Coxeter was born in Kensington to ...
Weyl groups and
point groups
In geometry, a point group is a mathematical group of symmetry operations ( isometries in a Euclidean space) that have a fixed point in common. The coordinate origin of the Euclidean space is conventionally taken to be a fixed point, and every ...
in the fourth dimension: the
simplex,
hypercube,
icositetrachoric, and
hexacosichoric groups; with the
demihypercube group generating two alternative constructions.
There are also
sixty-four (or 64 = 4
3) four-dimensional
Bravais lattices, ''and'' sixty-four
uniform polychora in the fourth dimension based on the same
,
,
and
Coxeter groups, and extending to
prismatic groups of
uniform polyhedra
In geometry, a uniform polyhedron has regular polygons as faces and is vertex-transitive (i.e., there is an isometry mapping any vertex onto any other). It follows that all vertices are congruent.
Uniform polyhedra may be regular (if also ...
, including one special
non-Wythoffian form, the
grand antiprism
In geometry, the grand antiprism or pentagonal double antiprismoid is a uniform 4-polytope (4-dimensional uniform polytope) bounded by 320 cells: 20 pentagonal antiprisms, and 300 tetrahedra. It is an anomalous, non-Wythoffian uniform 4-polytope ...
. There are also two infinite families of
duoprism
In geometry of 4 dimensions or higher, a double prism or duoprism is a polytope resulting from the Cartesian product of two polytopes, each of two dimensions or higher. The Cartesian product of an -polytope and an -polytope is an -polytope, wher ...
s and
antiprismatic prisms in the fourth dimension.
Four-dimensional
differential manifold
In mathematics, a differentiable manifold (also differential manifold) is a type of manifold that is locally similar enough to a vector space to allow one to apply calculus. Any manifold can be described by a collection of charts (atlas). One ma ...
s have some unique properties. There is only one
differential structure In mathematics, an ''n''-dimensional differential structure (or differentiable structure) on a set ''M'' makes ''M'' into an ''n''-dimensional differential manifold, which is a topological manifold with some additional structure that allows for dif ...
on
except when
=
, in which case there are uncountably many.
The smallest non-
cyclic group
In group theory, a branch of abstract algebra in pure mathematics, a cyclic group or monogenous group is a group, denoted C''n'', that is generated by a single element. That is, it is a set of invertible elements with a single associative bina ...
has four elements; it is the
Klein four-group. ''A''
alternating group
In mathematics, an alternating group is the group of even permutations of a finite set. The alternating group on a set of elements is called the alternating group of degree , or the alternating group on letters and denoted by or
Basic pr ...
s are not
simple for values
≤
.
Further extensions of the real numbers under
Hurwitz's theorem states that there are four
normed division algebras: the real numbers
, the
complex numbers
In mathematics, a complex number is an element of a number system that extends the real numbers with a specific element denoted , called the imaginary unit and satisfying the equation i^= -1; every complex number can be expressed in the form ...
, the
quaternions
, and the
octonions
. Under
Cayley–Dickson construction
In mathematics, the Cayley–Dickson construction, named after Arthur Cayley and Leonard Eugene Dickson, produces a sequence of algebras over the field of real numbers, each with twice the dimension of the previous one. The algebras produced b ...
s, the
sedenion
In abstract algebra, the sedenions form a 16-dimensional noncommutative and nonassociative algebra over the real numbers; they are obtained by applying the Cayley–Dickson construction to the octonions, and as such the octonions are isomorphic to ...
s
constitute a further fourth extension over
. The real numbers are
ordered,
commutative
In mathematics, a binary operation is commutative if changing the order of the operands does not change the result. It is a fundamental property of many binary operations, and many mathematical proofs depend on it. Most familiar as the name of ...
and
associative algebras
In mathematics, an algebra over a field (often simply called an algebra) is a vector space equipped with a bilinear product. Thus, an algebra is an algebraic structure consisting of a set together with operations of multiplication and addition ...
, as well as
alternative algebra In abstract algebra, an alternative algebra is an algebra in which multiplication need not be associative, only alternative. That is, one must have
*x(xy) = (xx)y
*(yx)x = y(xx)
for all ''x'' and ''y'' in the algebra.
Every associative algebra is o ...
s with
power-associativity. The complex numbers
share all four multiplicative algebraic properties of the reals
, without being ordered. The quaternions loose a further commutative algebraic property, while holding associative, alternative, and power-associative properties. The octonions are alternative and power-associative, while the sedenions are only power-associative. The sedenions and all further ''extensions'' of these four normed division algebras are solely power-associative with non-trivial
zero divisors, which makes them
non-division algebras.
has a
vector space of
dimension
In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coor ...
1, while
,
,
and
work in
algebraic number fields of dimensions 2, 4, 8, and 16, respectively.
List of basic calculations
Evolution of the Hindu-Arabic digit
Brahmic numerals represented 1, 2, and 3 with as many lines. 4 was simplified by joining its four lines into a cross that looks like the modern plus sign. The
Shunga would add a horizontal line on top of the digit, and the Kshatrapa and Pallava evolved the digit to a point where the speed of writing was a secondary concern. The
Arabs' 4 still had the early concept of the cross, but for the sake of efficiency, was made in one stroke by connecting the "western" end to the "northern" end; the "eastern" end was finished off with a curve. The Europeans dropped the finishing curve and gradually made the digit less cursive, ending up with a digit very close to the original Brahmin cross.
While the shape of the character for the digit 4 has an
ascender in most modern
typefaces, in typefaces with
text figures the glyph usually has a
descender, as, for example, in
.
On the
seven-segment display
A seven-segment display is a form of electronic display device for displaying decimal numerals that is an alternative to the more complex dot matrix displays.
Seven-segment displays are widely used in digital clocks, electronic meters, basic ...
s of pocket calculators and digital watches, as well as certain
optical character recognition fonts, 4 is seen with an open top.
Television station
A television station is a set of equipment managed by a business, organisation or other entity, such as an amateur television (ATV) operator, that transmits video content and audio content via radio waves directly from a transmitter on the eart ...
s that operate on
channel 4
Channel 4 is a British free-to-air public broadcast television network operated by the state-owned Channel Four Television Corporation. It began its transmission on 2 November 1982 and was established to provide a fourth television service ...
have occasionally made use of another variation of the "open 4", with the open portion being on the side, rather than the top. This version resembles the
Canadian Aboriginal syllabics letter ᔦ. The
magnetic ink character recognition
Magnetic ink character recognition code, known in short as MICR code, is a character recognition technology used mainly by the banking industry to streamline the processing and clearance of cheques and other documents. MICR encoding, called the ' ...
"CMC-7" font also uses this variety of "4".
In religion
Buddhism
*
Four Noble Truths –
Dukkha,
Samudaya,
Nirodha,
Magga
*
Four sights
The four sights are four events described in the legendary account of Gautama Buddha's life which led to his realization of the impermanence and the ultimate dissatisfaction of conditioned existence. According to this legend, before these encounte ...
– observations which affected Prince Siddhartha deeply and made him realize the sufferings of all beings, and compelled him to begin his spiritual journey—an
old man, a
sick man, a
dead
Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...
man, and an
ascetic
*
Four Great Elements –
earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
,
water
Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
,
fire
Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction products.
At a certain point in the combustion reaction, called the ignition point, flames a ...
, and
wind
*
Four Heavenly Kings
*
Four Foundations of Mindfulness – contemplation of the body, contemplation of feelings, contemplation of mind, contemplation of mental objects
*
Four Right Exertions
*
Four Bases of Power
*
Four jhānas
*
Four arūpajhānas
*
Four Divine Abidings –
loving-kindness,
compassion,
sympathetic joy, and
equanimity
*
Four stages of enlightenment
The four stages of awakening in Early Buddhism and Theravada
are four progressive stages culminating in full awakening (''Bodhi'') as an Arahant (SN 22.122).
These four stages are Sotāpanna, Sakadāgāmi, Anāgāmi, and Arahant. The oldest ...
–
stream-enterer,
once-returner,
non-returner, and
arahant
In Buddhism, an ''arhat'' (Sanskrit: अर्हत्) or ''arahant'' (Pali: अरहन्त्, 𑀅𑀭𑀳𑀦𑁆𑀢𑁆) is one who has gained insight into the true nature of existence and has achieved ''Nirvana'' and liberated ...
*
Four main pilgrimage sites –
Lumbini
Lumbinī ( ne, लुम्बिनी, IPA=ˈlumbini , "the lovely") is a Buddhist pilgrimage site in the Rupandehi District of Lumbini Province in Nepal. It is the place where, according to Buddhist tradition, Queen Mahamayadevi gave birth ...
,
Bodh Gaya,
Sarnath
Sarnath (Hindustani pronunciation: aːɾnaːtʰ also referred to as Sarangnath, Isipatana, Rishipattana, Migadaya, or Mrigadava) is a place located northeast of Varanasi, near the confluence of the Ganges and the Varuna rivers in Uttar Pr ...
, and
Kusinara
Judeo-Christian symbolism
*The
Tetragrammaton is the four-letter name of
God
In monotheistic thought, God is usually viewed as the supreme being, creator, and principal object of faith. Swinburne, R.G. "God" in Honderich, Ted. (ed)''The Oxford Companion to Philosophy'', Oxford University Press, 1995. God is typically ...
.
*
Ezekiel has a vision of four
living creatures: a man, a lion, an ox, and an eagle.
*The four Matriarchs (foremothers) of
Judaism
Judaism ( he, ''Yahăḏūṯ'') is an Abrahamic, monotheistic, and ethnic religion comprising the collective religious, cultural, and legal tradition and civilization of the Jewish people. It has its roots as an organized religion in t ...
are
Sarah,
Rebekah,
Leah, and
Rachel
Rachel () was a Biblical figure, the favorite of Jacob's two wives, and the mother of Joseph and Benjamin, two of the twelve progenitors of the tribes of Israel. Rachel's father was Laban. Her older sister was Leah, Jacob's first wife. Her aun ...
.
*The
Four Species (
lulav,
hadass,
aravah and
etrog) are taken as one of the
mitzvot on the
Jewish
Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
holiday of
Sukkot. (
Judaism
Judaism ( he, ''Yahăḏūṯ'') is an Abrahamic, monotheistic, and ethnic religion comprising the collective religious, cultural, and legal tradition and civilization of the Jewish people. It has its roots as an organized religion in t ...
)
*The Four Cups of Wine to drink on the
Jewish
Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
holiday of
Passover. (
Judaism
Judaism ( he, ''Yahăḏūṯ'') is an Abrahamic, monotheistic, and ethnic religion comprising the collective religious, cultural, and legal tradition and civilization of the Jewish people. It has its roots as an organized religion in t ...
)
*The Four Questions to be asked on the
Jewish
Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
holiday of
Passover. (
Judaism
Judaism ( he, ''Yahăḏūṯ'') is an Abrahamic, monotheistic, and ethnic religion comprising the collective religious, cultural, and legal tradition and civilization of the Jewish people. It has its roots as an organized religion in t ...
)
*The Four Sons to be dealt with on the
Jewish
Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
holiday of
Passover. (
Judaism
Judaism ( he, ''Yahăḏūṯ'') is an Abrahamic, monotheistic, and ethnic religion comprising the collective religious, cultural, and legal tradition and civilization of the Jewish people. It has its roots as an organized religion in t ...
)
*The Four Expressions of Redemption to be said on the
Jewish
Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
holiday of
Passover. (
Judaism
Judaism ( he, ''Yahăḏūṯ'') is an Abrahamic, monotheistic, and ethnic religion comprising the collective religious, cultural, and legal tradition and civilization of the Jewish people. It has its roots as an organized religion in t ...
)
*The four
Gospels:
Matthew,
Mark,
Luke, and
John
John is a common English name and surname:
* John (given name)
* John (surname)
John may also refer to:
New Testament
Works
* Gospel of John, a title often shortened to John
* First Epistle of John, often shortened to 1 John
* Secon ...
. (
Christianity
Christianity is an Abrahamic monotheistic religion based on the life and teachings of Jesus of Nazareth. It is the world's largest and most widespread religion with roughly 2.38 billion followers representing one-third of the global pop ...
)
*The
Four Horsemen of the Apocalypse
The Four Horsemen of the Apocalypse are figures in the Christian scriptures, first appearing in the Book of Revelation, a piece of apocalypse literature written by John of Patmos.
Revelation 6 tells of a book or scroll in God's right hand t ...
ride in the
Book of Revelation. (
Christianity
Christianity is an Abrahamic monotheistic religion based on the life and teachings of Jesus of Nazareth. It is the world's largest and most widespread religion with roughly 2.38 billion followers representing one-third of the global pop ...
)
*The
four holy cities of Judaism:
Jerusalem
Jerusalem (; he, יְרוּשָׁלַיִם ; ar, القُدس ) (combining the Biblical and common usage Arabic names); grc, Ἱερουσαλήμ/Ἰεροσόλυμα, Hierousalḗm/Hierosóluma; hy, Երուսաղեմ, Erusałēm. i ...
,
Hebron,
Safed, and
Tiberius
Hinduism
*There are four
Vedas
upright=1.2, The Vedas are ancient Sanskrit texts of Hinduism. Above: A page from the '' Atharvaveda''.
The Vedas (, , ) are a large body of religious texts originating in ancient India. Composed in Vedic Sanskrit, the texts constitute th ...
: Rigveda, Samaveda, Yajurveda and Atharvaveda.
*In
Puruṣārtha, there are four aims of human life:
Dharma,
Artha,
Kāma
''Kama'' (Sanskrit ) means "desire, wish, longing" in Hindu, Buddhist, Jain, and Sikh literature.Monier Williamsकाम, kāmaMonier-Williams Sanskrit English Dictionary, pp 271, see 3rd column Kama often connotes sensual pleasure, sexua ...
,
Moksha.
*The four stages of life
Brahmacharya (student life),
Grihastha (household life),
Vanaprastha (retired life) and
Sannyasa (renunciation).
*The four primary castes or strata of society:
Brahmana (priest/teacher),
Kshatriya (warrior/politician),
Vaishya (landowner/entrepreneur) and
Shudra
Shudra or ''Shoodra'' (Sanskrit: ') is one of the four '' varnas'' of the Hindu caste system and social order in ancient India. Various sources translate it into English as a caste, or alternatively as a social class. Theoretically, class ser ...
(servant/manual laborer).
*The
swastika symbol is traditionally used in
Hindu religions as a sign of good luck and signifies good from all four directions.
*The god
Brahma has four faces.
*There are four ''
yugas'': ''
Satya'', ''
Dvapara'', ''
Treta'' and ''
Kali''
Islam
*
Eid al-Adha
Eid al-Adha () is the second and the larger of the two main holidays celebrated in Islam (the other being Eid al-Fitr). It honours the willingness of Ibrahim (Abraham) to sacrifice his son Ismail (Ishmael) as an act of obedience to Allah's com ...
lasts for four days, from the 10th to the 14th of
Dhul Hijja.
*The
four holy cities of Islam: Mecca, Medina, Jerusalem and Damascus.
*The
four tombs in the Green Dome: Muhammad, Abu Bakr, Umar ibn Khattab and Isa ibn Maryam (Jesus).
*There are four
Rashidun or Rightly Guided
Caliphs:
Abu Bakr
Abu Bakr Abdallah ibn Uthman Abi Quhafa (; – 23 August 634) was the senior companion and was, through his daughter Aisha, a father-in-law of the Islamic prophet Muhammad, as well as the first caliph of Islam. He is known with the honor ...
,
Umar ibn al-Khattab,
Uthman ibn Affan and
Ali ibn Abi Talib.
*The Four
Arch Angels in Islam are: Jibraeel (Gabriel), Mikaeel (Michael), Izraeel (Azrael), and Israfil (Raphael)
*There are four months in which war is not permitted:
Muharram,
Rajab,
Dhu al-Qi'dah
Dhu al-Qa'dah ( ar, ذُو ٱلْقَعْدَة, ', ), also spelled Dhu al-Qi'dah or Zu al-Qa'dah, is the eleventh month in the Islamic calendar.
It could possibly mean "possessor or owner of the sitting and seating place" - the space occupied w ...
and
Dhu al-Hijjah.
*There are four
Sunni schools of
fiqh
''Fiqh'' (; ar, فقه ) is Islamic jurisprudence. Muhammad-> Companions-> Followers-> Fiqh.
The commands and prohibitions chosen by God were revealed through the agency of the Prophet in both the Quran and the Sunnah (words, deeds, and ...
:
Hanafi,
Shafi`i
The Shafii ( ar, شَافِعِي, translit=Shāfiʿī, also spelled Shafei) school, also known as Madhhab al-Shāfiʿī, is one of the four major traditional schools of religious law (madhhab) in the Sunnī branch of Islam. It was founded by ...
,
Maliki and
Hanbali.
*There are four major Sunni Imams:
Abū Ḥanīfa,
Muhammad ibn Idris ash-Shafi`i
Abū ʿAbdillāh Muḥammad ibn Idrīs al-Shāfiʿī ( ar, أَبُو عَبْدِ ٱللهِ مُحَمَّدُ بْنُ إِدْرِيسَ ٱلشَّافِعِيُّ, 767–19 January 820 CE) was an Arab Muslim theologian, writer, and schola ...
,
Malik ibn Anas
Malik ibn Anas ( ar, مَالِك بن أَنَس, 711–795 CE / 93–179 AH), whose full name is Mālik bin Anas bin Mālik bin Abī ʿĀmir bin ʿAmr bin Al-Ḥārith bin Ghaymān bin Khuthayn bin ʿAmr bin Al-Ḥārith al-Aṣbaḥī ...
and
Ahmad ibn Hanbal
Ahmad ibn Hanbal al-Dhuhli ( ar, أَحْمَد بْن حَنْبَل الذهلي, translit=Aḥmad ibn Ḥanbal al-Dhuhlī; November 780 – 2 August 855 CE/164–241 AH), was a Muslim jurist, theologian, ascetic, hadith traditionist, and ...
.
*There are four
books in Islam: Taurait, Zaboor, Injeel, Quran.
*Waiting for four months is ordained for those who take an oath for abstention from their wives.
*The waiting period of the woman whose husband dies is
four months and ten days.
*When Abraham said: "My Lord, show me how You give life to the dead," Allah said: "Why! Do you have no faith?" Abraham replied: "Yes, but in order that my heart be at rest." He said: "Then take four birds, and tame them to yourself, then put a part of them on every hill, and summon them; they will come to you flying.
l-Baqara 2:260*The respite of four months was granted to give time to the mushriks in Surah
At-Tawba
At-Tawbah ( ar, ٱلتوبة, ; The Repentance), also known as Bara'ah ( ar, براءة, ; Repudiation), is the ninth chapter ('' sūrah'') of the Quran. It contains 129 verses ('' āyāt'') and is one of the last Medinan surahs.
This Surah i ...
so that they should consider their position carefully and decide whether to make preparation for war or to emigrate from the country or to accept Islam.
*Those who accuse honorable women (of unchastity) but do not produce four witnesses, flog them with eighty lashes, and do not admit their testimony ever after. They are indeed transgressors.
n-Noor 24:4
Taoism
*
Four Symbols
The Four Symbols (, literally meaning "four images"), are four mythological creatures appearing among the Chinese constellations along the ecliptic, and viewed as the guardians of the four cardinal directions. These four creatures are also ref ...
of
I Ching
Other
*In a more general sense, numerous mythological and cosmogonical systems consider
Four corners of the world
Several cosmological and mythological systems portray four corners of the world or four quarters of the world corresponding approximately to the four points of the compass (or the two solstices and two equinoxes). At the center may lie a sacr ...
as essentially corresponding to the four points of the compass.
*Four is the sacred number of the
Zia, an indigenous tribe located in the U.S. state of
New Mexico.
*The Chinese, the Koreans, and the Japanese are
superstitious about the number four because it is a
homonym for "death" in their languages.
*In
Slavic mythology, the god
Svetovid has four heads.
In politics
*
Four Freedoms: four fundamental freedoms that
Franklin D. Roosevelt
Franklin Delano Roosevelt (; ; January 30, 1882April 12, 1945), often referred to by his initials FDR, was an American politician and attorney who served as the 32nd president of the United States from 1933 until his death in 1945. As the ...
declared ought to be enjoyed by everyone in the world: Freedom of Speech, Freedom of Religion, Freedom from Want, Freedom from Fear.
*
Gang of Four: Popular name for four Chinese Communist Party leaders who rose to prominence during China's Cultural Revolution, but were ousted in 1976 following the death of Chairman
Mao Zedong. Among the four was Mao's widow,
Jiang Qing
Jiang Qing (19 March 191414 May 1991), also known as Madame Mao, was a Chinese communist revolutionary, actress, and major political figure during the Cultural Revolution (1966–1976). She was the fourth wife of Mao Zedong, the Chairman of ...
. Since then, many other political factions headed by four people have been called "Gangs of Four".
In computing
*Four
bit
The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...
s (half a
byte) are sometimes called a
nibble.
In science
*A
tetramer is an
oligomer formed out of four sub-units.
In astronomy
*Four terrestrial (or rocky) planets in the
Solar System
The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
:
Mercury,
Venus,
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
, and
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
.
*Four giant gas/ice planets in the
Solar System
The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
:
Jupiter,
Saturn,
Uranus, and
Neptune.
*Four of Jupiter's moons (the
Galilean moons) are readily visible from Earth with a hobby telescope.
*
Messier object
The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters'').
Because Messier was only in ...
M4, a magnitude 7.5
globular cluster
A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...
in the constellation
Scorpius
Scorpius is a zodiac constellation located in the Southern celestial hemisphere, where it sits near the center of the Milky Way, between Libra to the west and Sagittarius to the east. Scorpius is an ancient constellation that pre-dates the Gr ...
.
*The Roman numeral IV stands for
subgiant
A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution ...
in the
Yerkes spectral classification scheme.
In biology
*Four is the number of
nucleobase types in
DNA and
RNA –
adenine,
guanine,
cytosine,
thymine (
uracil in
RNA).
*Many
chordates have four feet, legs or leglike appendages (
tetrapods
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct therapsi ...
).
*The
mammalian
heart consists of four chambers.
*Many
mammals (
Carnivora,
Ungulata) use four fingers for movement.
*All
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...
s with wings except
flies
Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced m ...
and some others have four
wings.
*Insects of the superorder
Endopterygota, also known as Holometabola, such as butterflies, ants, bees, beetles, fleas, flies, moths, and wasps, undergo
holometabolism—complete metamorphism in four stages—from (1) embryo (ovum, egg), to (2) larva (such as grub, caterpillar), then (3) pupa (such as the chrysalis), and finally (4) the imago.
*In the common
ABO blood group system
The ABO blood group system is used to denote the presence of one, both, or neither of the A and B antigens on erythrocytes. For human blood transfusions, it is the most important of the 43 different blood type (or group) classification system ...
, there are four blood types (A, B, O, AB).
*
Humans have four
canines and four
wisdom teeth
A third molar, commonly called wisdom tooth, is one of the three molars per quadrant of the human dentition. It is the most posterior of the three. The age at which wisdom teeth come through ( erupt) is variable, but this generally occurs betw ...
.
*The cow's stomach is divided in four digestive compartments: reticulum, rumen, omasum and abomasum.
In chemistry
*
Valency of
carbon (that is basis of life on the Earth) is four. Also because of its tetrahedral crystal bond structure,
diamond (one of the natural allotropes of carbon) is the hardest known naturally occurring material. It is also the valence of
silicon, whose compounds form the majority of the mass of the Earth's crust.
*The
atomic number of
beryllium
*There are four basic states of
matter
In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic part ...
:
solid,
liquid,
gas
Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma).
A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
, and
plasma.
In physics
*
Special relativity and
general relativity
General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...
treat nature as four-
dimension
In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coor ...
al:
3D regular
space and one-dimensional
time
Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, ...
are treated together and called
spacetime. Also, any event ''E'' has a
light cone
In special and general relativity, a light cone (or "null cone") is the path that a flash of light, emanating from a single event (localized to a single point in space and a single moment in time) and traveling in all directions, would take thro ...
composed of four zones of possible communication and cause and effect (outside the light cone is strictly incommunicado).
*There are four
fundamental forces
In physics, the fundamental interactions, also known as fundamental forces, are the interactions that do not appear to be reducible to more basic interactions. There are four fundamental interactions known to exist: the gravitational and electro ...
(
electromagnetism
In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of ...
,
gravitation, the
weak nuclear force, and the
strong nuclear force
The strong interaction or strong force is a fundamental interaction that confines quarks into proton, neutron, and other hadron particles. The strong interaction also binds neutrons and protons to create atomic nuclei, where it is called the ...
).
*In
statistical mechanics, the
four functions inequality is an inequality for four functions on a finite
distributive lattice
In mathematics, a distributive lattice is a lattice in which the operations of join and meet distribute over each other. The prototypical examples of such structures are collections of sets for which the lattice operations can be given by set ...
.
In logic and philosophy
*The symbolic meanings of the number four are linked to those of the cross and the square. "Almost from prehistoric times, the number four was employed to signify what was solid, what could be touched and felt. Its relationship to the cross (four points) made it an outstanding symbol of wholeness and universality, a symbol which drew all to itself". Where lines of latitude and longitude intersect, they divide the earth into four proportions. Throughout the world kings and chieftains have been called "lord of the four suns" or "lord of the four quarters of the earth", which is understood to refer to the extent of their powers both territorially and in terms of total control of their subjects' doings.
*The
Square of Opposition, in both its Aristotelian version and its
Boolean version, consists of four forms: A ("All ''S'' is ''R''"), I ("Some ''S'' is ''R''"), E ("No ''S'' is ''R''"), and O ("Some ''S'' is not ''R''").
*In regard to whether two given propositions can have the same
truth value, there are four separate logical possibilities: the propositions are ''subalterns'' (possibly both are true, and possibly both are false); ''subcontraries'' (both may be true, but not that both are false); ''contraries'' (both may be false, but not that both are true); or ''contradictories'' (it is not possible that both are true, and it is not possible that both are false).
*
Aristotle held that there are basically
four causes
The four causes or four explanations are, in Aristotelian thought, four fundamental types of answer to the question "why?", in analysis of change or movement in nature: the material, the formal, the efficient, and the final. Aristotle wrote th ...
in nature: the
material, the
formal, the
efficient, and the
final.
*The
Stoics held with four basic
categories
Category, plural categories, may refer to:
Philosophy and general uses
*Categorization, categories in cognitive science, information science and generally
*Category of being
* ''Categories'' (Aristotle)
*Category (Kant)
* Categories (Peirce)
* ...
, all viewed as bodies (substantial and insubstantial): (1) ''substance'' in the sense of substrate, primary formless matter; (2) ''quality'', matter's organization to differentiate and individualize something, and coming down to a physical ingredient such as ''pneuma'', breath; (3) ''somehow holding'' (or ''disposed''), as in a posture, state, shape, size, action, and (4) ''somehow holding'' (or ''disposed'') ''toward something,'' as in relative location, familial relation, and so forth.
*
Immanuel Kant expounded a
table of judgments involving four three-way alternatives, in regard to (1) Quantity, (2) Quality, (3) Relation, (4) Modality, and, based thereupon, a
table of four categories, named by the terms just listed, and each with three subcategories.
*
Arthur Schopenhauer's doctoral thesis was ''
On the Fourfold Root of the Principle of Sufficient Reason''.
*
Franz Brentano held that any major philosophical period has four phases: (1) Creative and rapidly progressing with scientific interest and results; then declining through the remaining phases, (2) practical, (3) increasingly skeptical, and (4) literary, mystical, and scientifically worthless—until philosophy is renewed through a new period's first phase. (See Brentano's essay "The Four Phases of Philosophy and Its Current State" 1895, tr. by Mezei and Smith 1998.)
*
C. S. Peirce, usually a
trichotomist, discussed four methods for overcoming troublesome uncertainties and achieving secure beliefs: (1) the method of tenacity (policy of sticking to initial belief), (2) the method of authority, (3) the method of congruity (following a fashionable
paradigm), and (4) the
fallibilistic, self-correcting method of science (see "
The Fixation of Belief", 1877); and four barriers to inquiry, barriers refused by the fallibilist: (1) assertion of absolute certainty; (2) maintaining that something is unknowable; (3) maintaining that something is inexplicable because absolutely basic or ultimate; (4) holding that perfect exactitude is possible, especially such as to quite preclude unusual and anomalous phenomena (see
F.R.L. irst Rule of Logic 1899).
*
Paul Weiss built a system involving four modes of being: Actualities (substances in the sense of substantial, spatiotemporally finite beings), Ideality or Possibility (pure normative form), Existence (the dynamic field), and God (unity). (See Weiss's ''Modes of Being'', 1958).
*
Karl Popper outlined a tetradic schema to describe the growth of theories and, via generalization, also the emergence of new behaviors and living organisms: (1) problem, (2) tentative theory, (3) (attempted) error-elimination (especially by way of critical discussion), and (4) new problem(s). (See Popper's ''Objective Knowledge'', 1972, revised 1979.)
*
John Boyd (military strategist) made his key concept the decision cycle or
OODA loop
The OODA loop is the cycle ''observe–orient–decide–act'', developed by military strategist and United States Air Force Colonel John Boyd. Boyd applied the concept to the combat operations process, often at the operational level during m ...
, consisting of four stages: (1) observation (data intake through the senses), (2) orientation (analysis and synthesis of data), (3) decision, and (4) action. Boyd held that his decision cycle has philosophical generality, though for strategists the point remains that, through swift decisions, one can disrupt an opponent's decision cycle.
*
Richard McKeon outlined four classes (each with four subclasses) of modes of philosophical inquiry: (1) Modes of Being (Being); (2) Modes of Thought (That which is); (3) Modes of Fact (Existence); (4) Modes of Simplicity (Experience)—and, corresponding to them, four classes (each with four subclasses) of philosophical semantics: Principles, Methods, Interpretations, and Selections. (See McKeon's "Philosophic Semantics and Philosophic Inquiry" in ''Freedom and History and Other Essays'', 1989.)
*
Jonathan Lowe (E.J. Lowe) argues in ''The Four-Category Ontology'', 2006, for four categories: ''kinds'' (substantial universals), ''attributes'' (relational universals and property-universals), ''objects'' (substantial particulars), and ''modes'' (relational particulars and property-particulars, also known as "
tropes"). (See Lowe's "Recent Advances in Metaphysics," 2001
Eprint
*Four opposed camps of the morality and nature of evil:
moral absolutism
Moral absolutism is an ethical view that some (potentially all) actions are intrinsically right or wrong. Stealing, for instance, might be considered to be always immoral, even if done for the well-being of others (e.g., stealing food to feed a ...
,
amoralism,
moral relativism, and
moral universalism.
In technology
*The
resin identification code
The ASTM International Resin Identification Coding System, often abbreviated RIC, is a set of symbols appearing on plastic products that identify the plastic resin out of which the product is made. It was developed in 1988 by the Society of t ...
used in recycling to identify
low-density polyethylene
Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization. Its ...
.
*Most
furniture has four legs – tables, chairs, etc.
*The
four color process (
CMYK) is used for
printing.
*Wide use of
rectangles (with four angles and four sides) because they have effective form and capability for close adjacency to each other (houses, rooms, tables, bricks, sheets of paper, screens, film frames).
*In the
Rich Text Format specification, language code 4 is for the
Chinese language
Chinese (, especially when referring to written Chinese) is a group of languages spoken natively by the ethnic Han Chinese majority and many minority ethnic groups in Greater China. About 1.3 billion people (or approximately 16% of the ...
. Codes for regional variants of Chinese are congruent to .
*
Credit card machines have four-twelve function keys.
*On most phones, the 4 key is associated with the letters
G,
H, and
I, but on the
BlackBerry Pearl, it is the key for
D and
F.
*On many
computer keyboards, the "4" key may also be used to type the
dollar sign
The dollar sign, also known as peso sign, is a symbol consisting of a capital " S" crossed with one or two vertical strokes ($ or ), used to indicate the unit of various currencies around the world, including most currencies denominated "p ...
($) if the
shift key
The Shift key is a modifier key on a keyboard, used to type capital letters and other alternate "upper" characters. There are typically two shift keys, on the left and right sides of the row below the home row. The Shift key's name originated f ...
is held down.
*It is the number of
bit
The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...
s in a
nibble, equivalent to half a
byte
*In
internet slang, "4" can replace the word "for" (as "four" and "for" are pronounced similarly). For example, typing "4u" instead of "for you".
*In
Leetspeak, "4" may be used to replace the letter "A".
*The
TCP/IP stack
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...
consists of four layers.
In transport
*Many
internal combustion engines
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combust ...
are called
four-stroke engines because they complete one thermodynamic cycle in four distinct steps: Intake, compression, power, and exhaust.
*Most
vehicle
A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), ...
s, including
motor vehicles, and particularly
cars/automobiles and light
commercial vehicle
A commercial vehicle is any type of motor vehicle used for transporting goods or paying passengers.
The United States defines a "commercial motor vehicle" as any self-propelled or towed vehicle used on a public highway in interstate commerce to t ...
s have four road
wheels.
*"
Quattro", meaning four in the Italian language, is used by
Audi
Audi AG () is a German automotive manufacturer of luxury vehicles headquartered in Ingolstadt, Bavaria, Germany. As a subsidiary of its parent company, the Volkswagen Group, Audi produces vehicles in nine production facilities worldwide.
Th ...
as a trademark to indicate that
all-wheel drive (AWD) technologies are used on Audi-branded cars. The word "Quattro" was initially used by Audi in 1980 in its original 4WD coupé, the
Audi Quattro. Audi also has a privately held subsidiary company called
quattro GmbH.
*
List of highways numbered 4
Route 4, or Highway 4, may refer to several highways in the following countries:
International
* AH4, Asian Highway 4
* European route E04
* European route E004
* Cairo – Cape Town Highway
Albania
* SH-4 road in Albania from Durres to Kakav ...
In sports
* In the
Australian Football League, the top level of
Australian rules football, each team is allowed 4 "
interchanges" (substitute players), who can be freely substituted at any time, subject to a limit on the total number of substitutions.
*In
baseball
Baseball is a bat-and-ball sport played between two teams of nine players each, taking turns batting and fielding. The game occurs over the course of several plays, with each play generally beginning when a player on the fielding t ...
:
**There are four bases in the game:
first base,
second base,
third base, and
home plate
A baseball field, also called a ball field or baseball diamond, is the field upon which the game of baseball is played. The term can also be used as a metonym for a baseball park. The term sandlot is sometimes used, although this usually refers ...
; to score a run, an offensive player must complete, in the sequence shown, a circuit of those four bases.
** When a batter receives four pitches that the umpire declares to be "
balls" in a single at-bat, a
base on balls, informally known as a "walk", is awarded, with the batter sent to first base.
**For scoring, number 4 is assigned to the
second baseman.
**Four is the most runs that can be scored on any single at bat, whereby all three baserunners and the batter score (the most common being via a
grand slam
Grand Slam most often refers to:
* Grand Slam (tennis), one player or pair winning all four major annual tournaments, or the tournaments themselves
Grand Slam or Grand slam may also refer to:
Games and sports
* Grand slam, winning category te ...
).
**The fourth batter in the batting lineup is called the
cleanup hitter.
*In
basketball
Basketball is a team sport in which two teams, most commonly of five players each, opposing one another on a rectangular court, compete with the primary objective of shooting a basketball (approximately in diameter) through the defender's h ...
, the number four is used to designate the
power forward
The power forward (PF), also known as the four, is one of the five traditional positions in a regulation basketball game. Traditionally, power forwards have played a role similar to centers. When on offense, they typically play with their ba ...
position, often referred to as "the four spot" or "the four".
*In
cricket
Cricket is a bat-and-ball game played between two teams of eleven players on a field at the centre of which is a pitch with a wicket at each end, each comprising two bails balanced on three stumps. The batting side scores runs by str ...
, a four is a specific type of scoring event, whereby the ball crosses the
boundary
Boundary or Boundaries may refer to:
* Border, in political geography
Entertainment
* ''Boundaries'' (2016 film), a 2016 Canadian film
* ''Boundaries'' (2018 film), a 2018 American-Canadian road trip film
*Boundary (cricket), the edge of the pla ...
after touching the ground at least one time, scoring four runs. Taking four wickets in four consecutive balls is typically referred to as a double hat trick (two consecutive, overlapping hat tricks).
*In
American Football teams get four downs to reach the line of gain.
*In
rowing
Rowing is the act of propelling a human-powered watercraft using the sweeping motions of oars to displace water and generate reactional propulsion. Rowing is functionally similar to paddling, but rowing requires oars to be mechanically ...
, a four refers to a
boat for four rowers, with or without
coxswain
The coxswain ( , or ) is the person in charge of a boat, particularly its navigation and steering. The etymology of the word gives a literal meaning of "boat servant" since it comes from ''cock'', referring to the cockboat, a type of ship's boa ...
. In rowing nomenclature, 4− represents a coxless four and 4+ represents a coxed four.
*In
rugby league:
** A
try
Try or TRY may refer to:
Music Albums
* ''Try!'', an album by the John Mayer Trio
* ''Try'' (Bebo Norman album) (2014) Songs
* "Try" (Blue Rodeo song) (1987)
* "Try" (Colbie Caillat song) (2014)
* "Try" (Nelly Furtado song) (2004)
* " Try (Ju ...
is worth 4 points.
** One of the two starting centres wears the jersey number 4. (An exception to this rule is the
Super League, which uses static squad numbering.)
*In
rugby union:
** One of the two starting
locks
Lock(s) may refer to:
Common meanings
*Lock and key, a mechanical device used to secure items of importance
*Lock (water navigation), a device for boats to transit between different levels of water, as in a canal
Arts and entertainment
* ''Lock ...
wears the jersey number 4.
** In the standard
bonus points system, a point is awarded in the league standings to a team that scores at least 4 tries in a match, regardless of the match result.
In other fields
* The phrase "
four-letter word
The phrase four-letter word refers to a set of English-language words written with four letters which are considered profane, including common popular or slang terms for excretory functions, sexual activity and genitalia, blasphemies, terms ...
" is used to describe many
swear words in the
English language
English is a West Germanic language of the Indo-European language family, with its earliest forms spoken by the inhabitants of early medieval England. It is named after the Angles, one of the ancient Germanic peoples that migrated to the ...
.
*Four is the only number whose name in English has the same number of letters as its value.
*Four (, formal writing: ,
pinyin
Hanyu Pinyin (), often shortened to just pinyin, is the official romanization system for Standard Chinese, Standard Mandarin Chinese in China, and to some extent, in Singapore and Malaysia. It is often used to teach Mandarin, normally writte ...
sì) is considered an
unlucky number in
Chinese,
Korean
Korean may refer to:
People and culture
* Koreans, ethnic group originating in the Korean Peninsula
* Korean cuisine
* Korean culture
* Korean language
**Korean alphabet, known as Hangul or Chosŏn'gŭl
**Korean dialects and the Jeju language
** ...
,
Vietnamese
Vietnamese may refer to:
* Something of, from, or related to Vietnam, a country in Southeast Asia
** A citizen of Vietnam. See Demographics of Vietnam.
* Vietnamese people, or Kinh people, a Southeast Asian ethnic group native to Vietnam
** Overse ...
and
Japanese
Japanese may refer to:
* Something from or related to Japan, an island country in East Asia
* Japanese language, spoken mainly in Japan
* Japanese people, the ethnic group that identifies with Japan through ancestry or culture
** Japanese diaspor ...
cultures mostly in Eastern Asia because it sounds like the word "death" (,
pinyin
Hanyu Pinyin (), often shortened to just pinyin, is the official romanization system for Standard Chinese, Standard Mandarin Chinese in China, and to some extent, in Singapore and Malaysia. It is often used to teach Mandarin, normally writte ...
sǐ). To avoid complaints from people with tetraphobia, many numbered product lines skip the "four": e.g.
Nokia cell phones
A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whi ...
(there was no series beginning with a 4 until the
Nokia 4.2),
Palm
Palm most commonly refers to:
* Palm of the hand, the central region of the front of the hand
* Palm plants, of family Arecaceae
**List of Arecaceae genera
* Several other plants known as "palm"
Palm or Palms may also refer to:
Music
* Palm (ba ...
PDAs, etc. Some buildings skip floor 4 or replace the number with the letter "F", particularly in heavily Asian areas. ''See
tetraphobia'' and ''
Numbers in Chinese culture
Some numbers are believed by some to be auspicious or lucky (吉利, ) or inauspicious or unlucky (不吉, ) based on the Chinese word that the number sounds similar to. The numbers 3, 6, and 8 are generally considered to be lucky, while 4 is ...
''.
*In Pythagorean
numerology (a
pseudocience) the number 4 represents security and stability.
*The number of characters in a canonical
four-character idiom.
*In the
NATO phonetic alphabet, the digit 4 is called "fower".
*In
astrology,
Cancer
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
is the 4th
astrological sign
In Western astrology, astrological signs are the twelve 30-degree sectors that make up Earth's 360-degree orbit around the Sun. The signs enumerate from the first day of spring, known as the First Point of Aries, which is the vernal equinox. ...
of the
Zodiac.
*In
Tarot,
The Emperor is the fourth
trump
Trump most commonly refers to:
* Donald Trump (born 1946), 45th president of the United States (2017–2021)
* Trump (card games), any playing card given an ad-hoc high rank
Trump may also refer to:
Businesses and organizations
* Donald J. T ...
or
Major Arcana card.
*In ''
Tetris
''Tetris'' (russian: link=no, Тетрис) is a puzzle video game created by Soviet software engineer Alexey Pajitnov in 1984. It has been published by several companies for multiple platforms, most prominently during a dispute over the appro ...
'', a game named for the Greek word for 4, every shape in the game is formed of 4 blocks each.
*4 represents the number of Justices on the
Supreme Court of the United States necessary to grant a writ of
certiorari (i.e., agree to hear a case; it is one less than the number necessary to render a majority decision) at the court's current size.
*Number Four is a character in the book series ''
Lorien Legacies
''Lorien Legacies'' is a series of young adult science fiction books, written by James Frey, Jobie Hughes, and formerly, Greg Boose, under the collective pseudonym Pittacus Lore.
Lorien Legacies
''I am Number Four''
The first book of The ...
.''
*In the
performing arts, the
fourth wall
The fourth wall is a performance convention in which an invisible, imaginary wall separates actors from the audience. While the audience can see through this ''wall'', the convention assumes the actors act as if they cannot. From the 16th cen ...
is an imaginary barrier which separates the audience from the performers, and is "broken" when performers communicate directly to the audience.
In music
*In
written music,
common time
The time signature (also known as meter signature, metre signature, or measure signature) is a notational convention used in Western musical notation to specify how many beats (pulses) are contained in each measure (bar), and which note val ...
is constructed of four beats per measure and a quarter note receives one beat.
*In popular or
modern music, the most common
time signature is also founded on four beats, i.e., 4/4 having four
quarter note
A quarter note (American) or crotchet ( ) (British) is a musical note played for one quarter of the duration of a whole note (or semibreve). Quarter notes are notated with a filled-in oval note head and a straight, flagless stem. The stem ...
beats.
*The common
major scale
The major scale (or Ionian mode) is one of the most commonly used musical scales, especially in Western music. It is one of the diatonic scales. Like many musical scales, it is made up of seven notes: the eighth duplicates the first at double ...
is built on two sets of four notes (e.g., CDEF, GABC), where the first and last notes create an
octave interval (a pair-of-four relationship).
*The interval of a
perfect fourth
A fourth is a musical interval encompassing four staff positions in the music notation of Western culture, and a perfect fourth () is the fourth spanning five semitones (half steps, or half tones). For example, the ascending interval from C to ...
is a foundational element of many genres of music, represented in
music theory as the
tonic and
subdominant relationship. Four is also embodied within the
circle of fifths
In music theory, the circle of fifths is a way of organizing the 12 chromatic pitches as a sequence of perfect fifths. (This is strictly true in the standard 12-tone equal temperament system — using a different system requires one interval of ...
(also known as circle of fourths), which reveals the interval of four in more active harmonic contexts.
*The typical number of movements in a
symphony.
*The number of completed, numbered symphonies by
Johannes Brahms.
*The number of strings on a
violin
The violin, sometimes known as a '' fiddle'', is a wooden chordophone ( string instrument) in the violin family. Most violins have a hollow wooden body. It is the smallest and thus highest-pitched instrument ( soprano) in the family in regu ...
, a
viola, a
cello,
double bass
The double bass (), also known simply as the bass () (or by other names), is the largest and lowest-pitched bowed (or plucked) string instrument in the modern symphony orchestra (excluding unorthodox additions such as the octobass). Similar i ...
, a
cuatro
Cuatro is Spanish (and other Romance languages) for the number four.
Cuatro may also refer to:
* Cuatro (instrument), name for two distinct Latin American instruments, one from Puerto Rico (see Cuatro) and the other from Venezuela (see Cuatro) ...
, a typical
bass guitar, and a
ukulele, and the number of string pairs on a
mandolin.
*"Four calling birds" is the gift on the fourth day of Christmas in the carol "
The Twelve Days of Christmas".
Groups of four
*
Big Four (disambiguation)
*Four basic operations of arithmetic:
addition,
subtraction,
multiplication,
division
Division or divider may refer to:
Mathematics
*Division (mathematics), the inverse of multiplication
*Division algorithm, a method for computing the result of mathematical division
Military
*Division (military), a formation typically consisting ...
.
*
Greek classical elements (
fire
Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction products.
At a certain point in the combustion reaction, called the ignition point, flames a ...
,
air
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...
,
water
Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
,
earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
).
*
Four seasons:
spring,
summer,
autumn,
winter
Winter is the coldest season of the year in polar and temperate climates. It occurs after autumn and before spring. The tilt of Earth's axis causes seasons; winter occurs when a hemisphere is oriented away from the Sun. Different cultur ...
.
*
The Four Seasons (disambiguation)
*A
leap year generally occurs every four years.
*Approximately four weeks (4 times 7 days) to a lunar month (
synodic month
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
Variations
In Shona, Middle Eastern, and Euro ...
= 29.53 days). Thus the number four is universally an integral part of primitive sacred calendars.
*Four weeks of
Advent (and four
Advent candle
An Advent candle is a candle marked with the days of December up to Christmas Eve. It is typically used in a household rather than a church setting: each day in December the candle is burnt down a little more, to the mark for the day, to show t ...
s on the
Advent wreath
The Advent wreath, or Advent crown, is a Christian tradition that symbolizes the passage of the four weeks of Advent in the liturgical calendar of the Western church. It is traditionally a Lutheran practice, although it has spread to many other ...
).
*Four
cardinal directions
The four cardinal directions, or cardinal points, are the four main compass directions: north, east, south, and west, commonly denoted by their initials N, E, S, and W respectively. Relative to north, the directions east, south, and west are at ...
:
north,
south,
east
East or Orient is one of the four cardinal directions or points of the compass. It is the opposite direction from west and is the direction from which the Sun rises on the Earth.
Etymology
As in other languages, the word is formed from the fac ...
,
west.
*
Four Temperaments:
sanguine
Sanguine () or red chalk is chalk of a reddish-brown colour, so called because it resembles the colour of dried blood. It has been popular for centuries for drawing (where white chalk only works on coloured paper). The word comes via French fr ...
,
choleric,
melancholic,
phlegmatic.
*
Four Humors:
blood,
yellow bile
Humorism, the humoral theory, or humoralism, was a system of medicine detailing a supposed makeup and workings of the human body, adopted by Ancient Greek and Roman physicians and philosophers.
Humorism began to fall out of favor in the 1850s ...
,
black bile
Melancholia or melancholy (from el, µέλαινα χολή ',Burton, Bk. I, p. 147 meaning black bile) is a concept found throughout ancient, medieval and premodern medicine in Europe that describes a condition characterized by markedly dep ...
,
phlegm.
*
Four Great Ancient Capitals of China
This is a list of historical capitals of China.
Four Great Ancient Capitals
There are traditionally four major historical capitals of China referred to as the "Four Great Ancient Capitals of China" (). The four are Beijing, Nanjing, Luoyang and ...
.
*
Four-corner method.
*
Four Asian Tigers
The Four Asian Tigers (also known as the Four Asian Dragons or Four Little Dragons in Chinese and Korean) are the developed East Asian economies of Hong Kong, Singapore, South Korea, and Taiwan. Between the early 1960s and 1990s, they underwent ...
, referring to the economies of
Hong Kong,
Taiwan
Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...
,
South Korea
South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korean Peninsula and sharing a land border with North Korea. Its western border is formed by the Yellow Sea, while its eas ...
, and
Singapore
Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, bor ...
*
Cardinal principles.
*
Four cardinal virtues: justice, prudence, temperance, fortitude.
*Four
suits of
playing cards: hearts, diamonds, clubs, spades.
*Four
nation
A nation is a community of people formed on the basis of a combination of shared features such as language, history, ethnicity, culture and/or society. A nation is thus the collective Identity (social science), identity of a group of people unde ...
s of the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
: England,
Wales
Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...
,
Scotland
Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...
,
Northern Ireland
Northern Ireland ( ga, Tuaisceart Éireann ; sco, label= Ulster-Scots, Norlin Airlann) is a part of the United Kingdom, situated in the north-east of the island of Ireland, that is variously described as a country, province or region. Nort ...
.
*Four
provinces of Ireland:
Munster,
Ulster,
Leinster,
Connacht.
*Four estates:
politics
Politics (from , ) is the set of activities that are associated with making decisions in groups, or other forms of power relations among individuals, such as the distribution of resources or status. The branch of social science that stud ...
,
administration,
judiciary,
journalism. Especially in the expression "
Fourth Estate", which means journalism.
*
Four Corners is the only location in the United States where four
states come together at a single point:
Colorado
Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...
,
Utah,
New Mexico, and
Arizona
Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
.
*
Four Evangelists –
Matthew,
Mark,
Luke, and
John
John is a common English name and surname:
* John (given name)
* John (surname)
John may also refer to:
New Testament
Works
* Gospel of John, a title often shortened to John
* First Epistle of John, often shortened to 1 John
* Secon ...
* Four
Doctors of Western Church – Saint
Gregory the Great
Pope Gregory I ( la, Gregorius I; – 12 March 604), commonly known as Saint Gregory the Great, was the bishop of Rome from 3 September 590 to his death. He is known for instigating the first recorded large-scale mission from Rome, the Gregoria ...
, Saint
Ambrose, Saint
Augustine, and Saint
Jerome
* Four Doctors of Eastern Church –
Saint John Chrysostom
John Chrysostom (; gr, Ἰωάννης ὁ Χρυσόστομος; 14 September 407) was an important Early Church Father who served as archbishop of Constantinople. He is known for his preaching and public speaking, his denunciation of abu ...
,
Saint Basil the Great
Basil of Caesarea, also called Saint Basil the Great ( grc, Ἅγιος Βασίλειος ὁ Μέγας, ''Hágios Basíleios ho Mégas''; cop, Ⲡⲓⲁⲅⲓⲟⲥ Ⲃⲁⲥⲓⲗⲓⲟⲥ; 330 – January 1 or 2, 379), was a bishop of Cae ...
, and
Gregory of Nazianzus and
Saint Athanasius
* Four
Galilean moons of Jupiter –
Io,
Europa,
Ganymede, and
Callisto Callisto most commonly refers to:
*Callisto (mythology), a nymph
*Callisto (moon), a moon of Jupiter
Callisto may also refer to:
Art and entertainment
*''Callisto series'', a sequence of novels by Lin Carter
*''Callisto'', a novel by Torsten Kro ...
* The
Gang of Four was a
Chinese communist political faction.
* The
Fantastic Four: Mr. Fantastic, The Invisible Woman, The Human Torch, The Thing.
* The
Teenage Mutant Ninja Turtles
''Teenage Mutant Ninja Turtles'' is an American media franchise created by the comic book artists Kevin Eastman and Peter Laird. It follows Leonardo, Michelangelo, Donatello and Raphael, four anthropomorphic turtle brothers (named after It ...
: Leonardo, Michelangelo, Donatello, Raphael
*
The Beatles
The Beatles were an English rock band, formed in Liverpool in 1960, that comprised John Lennon, Paul McCartney, George Harrison and Ringo Starr. They are regarded as the most influential band of all time and were integral to the developmen ...
were also known as the "Fab Four": John Lennon, Paul McCartney, George Harrison, Ringo Starr.
*
Gang of Four is a British
post-punk rock band formed in the late 1970s.
* Four rivers in the
Garden of Eden (
Genesis 2:10–14):
Pishon (perhaps the Jaxartes or
Syr Darya),
Gihon
Gihon is the name of the second river mentioned in the second chapter of the biblical Book of Genesis. The Gihon is mentioned as one of four rivers (along with the Tigris, Euphrates, and Pishon) issuing out of the Garden of Eden that branched fr ...
(perhaps the Oxus or
Amu Darya), Hiddekel (
Tigris), and P'rat (
Euphrates).
* There are also four years in a single
Olympiad
An olympiad ( el, Ὀλυμπιάς, ''Olympiás'') is a period of four years, particularly those associated with the ancient and modern Olympic Games.
Although the ancient Olympics were established during Greece's Archaic Era, it was not unti ...
(duration between the
Olympic Games). Many major international sports competitions follow this cycle, among them the
FIFA World Cup
The FIFA World Cup, often simply called the World Cup, is an international association football competition contested by the senior men's national teams of the members of the ' ( FIFA), the sport's global governing body. The tournament ha ...
and its
women's version, the FIBA World Championships for
men
A man is an adult male human. Prior to adulthood, a male human is referred to as a boy (a male child or adolescent). Like most other male mammals, a man's genome usually inherits an X chromosome from the mother and a Y chro ...
and
women, and the
Rugby World Cup.
* There are four limbs on the
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...
body.
* Four Houses of
Hogwarts
Hogwarts School of Witchcraft and Wizardry () is a fictional Scotland, Scottish boarding school of Magic in Harry Potter, magic for students aged eleven to eighteen, and is the primary setting for the first six books in J. K. Rowling's ''Harry Pot ...
in the
Harry Potter series: Gryffindor, Hufflepuff, Ravenclaw, Slytherin.
* Four known continents of the world in the ''
A Song of Ice and Fire'' series: Westeros, Essos, Sothoryos, Ulthos.
* Each Grand Prix in
Nintendo's ''
Mario Kart'' series is divided into four cups and each cup is divided into four courses. The Mushroom Cup, Flower Cup, Star Cup, and Special Cup make up the Nitro Grand Prix, while the Shell Cup, Banana Cup, Leaf Cup, and the Lightning Cup make up the Retro Grand Prix.
See also
*
List of highways numbered 4
Route 4, or Highway 4, may refer to several highways in the following countries:
International
* AH4, Asian Highway 4
* European route E04
* European route E004
* Cairo – Cape Town Highway
Albania
* SH-4 road in Albania from Durres to Kakav ...
References
*Wells, D. ''
The Penguin Dictionary of Curious and Interesting Numbers
''The Penguin Dictionary of Curious and Interesting Numbers'' is a reference book for recreational mathematics and elementary number theory written by David Wells. The first edition was published in paperback by Penguin Books in 1986 in the UK, ...
'' London: Penguin Group. (1987): 55–58
External links
Marijn.Org on Why is everything four? by Penelope Merritt at samuel-beckett.net
The Number 4The Positive Integer 4
{{Authority control
Integers