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8 (eight) is the
natural number In mathematics, the natural numbers are those numbers used for counting (as in "there are ''six'' coins on the table") and ordering (as in "this is the ''third'' largest city in the country"). Numbers used for counting are called '' cardinal ...
following 7 and preceding 9.


In mathematics

8 is: * a
composite number A composite number is a positive integer that can be formed by multiplying two smaller positive integers. Equivalently, it is a positive integer that has at least one divisor In mathematics, a divisor of an integer n, also called a factor ...
, its
proper divisor In mathematics, a divisor of an integer n, also called a factor of n, is an integer m that may be multiplied by some integer to produce n. In this case, one also says that n is a multiple of m. An integer n is divisible or evenly divisible by ...
s being , , and . It is twice 4 or four times 2. * a
power of two A power of two is a number of the form where is an integer, that is, the result of exponentiation with number two as the base and integer  as the exponent. In a context where only integers are considered, is restricted to non-negat ...
, being 2 (two cubed), and is the first number of the form , being an integer greater than 1. * the first number which is neither
prime A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways ...
nor
semiprime In mathematics, a semiprime is a natural number that is the product of exactly two prime numbers. The two primes in the product may equal each other, so the semiprimes include the squares of prime numbers. Because there are infinitely many prime ...
. * the base of the
octal The octal numeral system, or oct for short, is the radix, base-8 number system, and uses the Numerical digit, digits 0 to 7. This is to say that 10octal represents eight and 100octal represents sixty-four. However, English, like most languages, ...
number system, which is mostly used with
computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These prog ...
s. In octal, one digit represents three bits. In modern computers, a
byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...
is a grouping of eight bits, also called an
octet Octet may refer to: Music * Octet (music), ensemble consisting of eight instruments or voices, or composition written for such an ensemble ** String octet, a piece of music written for eight string instruments *** Octet (Mendelssohn), 1825 com ...
. * a
Fibonacci number In mathematics, the Fibonacci numbers, commonly denoted , form a sequence, the Fibonacci sequence, in which each number is the sum of the two preceding ones. The sequence commonly starts from 0 and 1, although some authors start the sequence from ...
, being plus . The next Fibonacci number is . 8 is the only positive Fibonacci number, aside from 1, that is a perfect cube. * the only nonzero perfect power that is one less than another perfect power, by
Mihăilescu's Theorem Catalan's conjecture (or Mihăilescu's theorem) is a theorem in number theory that was conjectured by the mathematician Eugène Charles Catalan in 1844 and proven in 2002 by Preda Mihăilescu at Paderborn University. The integers 23 and 32 are ...
. * the order of the smallest non-abelian group all of whose subgroups are normal. * the dimension of the
octonion In mathematics, the octonions are a normed division algebra over the real numbers, a kind of hypercomplex number system. The octonions are usually represented by the capital letter O, using boldface or blackboard bold \mathbb O. Octonions hav ...
s and is the highest possible dimension of a normed division algebra. * the first number to be the aliquot sum of two numbers other than itself; the discrete biprime , and the square number . A number is divisible by 8 if its last three digits, when written in
decimal The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hindu–Arabic numeral ...
, are also divisible by 8, or its last three digits are 0 when written in binary. A
polygon In geometry, a polygon () is a plane figure that is described by a finite number of straight line segments connected to form a closed '' polygonal chain'' (or ''polygonal circuit''). The bounded plane region, the bounding circuit, or the two ...
with eight sides is an
octagon In geometry, an octagon (from the Greek ὀκτάγωνον ''oktágōnon'', "eight angles") is an eight-sided polygon or 8-gon. A '' regular octagon'' has Schläfli symbol and can also be constructed as a quasiregular truncated square, t, w ...
. The sides and
span Span may refer to: Science, technology and engineering * Span (unit), the width of a human hand * Span (engineering), a section between two intermediate supports * Wingspan, the distance between the wingtips of a bird or aircraft * Sorbitan ester ...
of a regular octagon, or truncated
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 ...
, are in silver ratio, and its circumscribing
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 ...
has a side and diagonal length ratio of ; with both the silver ratio and the
square root of two The square root of 2 (approximately 1.4142) is a positive real number that, when multiplied by itself, equals the number 2. It may be written in mathematics as \sqrt or 2^, and is an algebraic number. Technically, it should be called the princi ...
intimately interconnected through
Pell number In mathematics, the Pell numbers are an infinite sequence of integers, known since ancient times, that comprise the denominators of the closest rational approximations to the square root of 2. This sequence of approximations begins , , , , an ...
s, where in particular the quotient of successive Pell numbers generates rational approximations for coordinates of a regular octagon. With a
central angle A central angle is an angle whose apex (vertex) is the center O of a circle and whose legs (sides) are radii intersecting the circle in two distinct points A and B. Central angles are subtended by an arc between those two points, and the arc le ...
of 45 degrees and an
internal angle In geometry, an angle of a polygon is formed by two sides of the polygon that share an endpoint. For a simple (non-self-intersecting) polygon, regardless of whether it is convex or non-convex, this angle is called an interior angle (or ) if ...
of 135 degrees, regular octagons are able to
tessellate A tessellation or tiling is the covering of a surface, often a plane, using one or more geometric shapes, called ''tiles'', with no overlaps and no gaps. In mathematics, tessellation can be generalized to higher dimensions and a variety of ...
two-dimensional space alongside squares in the
truncated square tiling In geometry, the truncated square tiling is a semiregular tiling, semiregular tiling by regular polygons of the Euclidean plane with one square (geometry), square and two octagons on each vertex (geometry), vertex. This is the only edge-to-edge ti ...
, as well as fill a plane-vertex with a regular
triangle A triangle is a polygon with three edges and three vertices. It is one of the basic shapes in geometry. A triangle with vertices ''A'', ''B'', and ''C'' is denoted \triangle ABC. In Euclidean geometry, any three points, when non- colline ...
and a regular
icositetragon In geometry, an icositetragon (or icosikaitetragon) or 24-gon is a twenty-four-sided polygon. The sum of any icositetragon's interior angles is 3960 degrees. Regular icositetragon The '' regular icositetragon'' is represented by Schläfli symbol ...
. The
Ammann–Beenker tiling In geometry, an Ammann–Beenker tiling is a nonperiodic tiling which can be generated either by an aperiodic set of prototiles as done by Robert Ammann in the 1970s, or by the cut-and-project method as done independently by F. P. M. Beenker. ...
is a nonperiodic tesselation of prototiles that feature prominent octagonal ''silver'' eightfold symmetry, and is the two-dimensional
orthogonal projection In linear algebra and functional analysis, a projection is a linear transformation P from a vector space to itself (an endomorphism) such that P\circ P=P. That is, whenever P is applied twice to any vector, it gives the same result as if it wer ...
of the
8-8 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 ...
. In number theory,
figurate number The term figurate number is used by different writers for members of different sets of numbers, generalizing from triangular numbers to different shapes (polygonal numbers) and different dimensions (polyhedral numbers). The term can mean * polyg ...
s representing octagons are called octagonal numbers. A
cube In geometry, a cube is a three-dimensional solid object bounded by six square faces, facets or sides, with three meeting at each vertex. Viewed from a corner it is a hexagon and its net is usually depicted as a cross. The cube is the only ...
is a regular polyhedron with eight vertices that also forms the
cubic honeycomb The cubic honeycomb or cubic cellulation is the only proper regular space-filling tessellation (or honeycomb) in Euclidean 3-space made up of cubic cells. It has 4 cubes around every edge, and 8 cubes around each vertex. Its vertex figure is a r ...
, the only regular honeycomb in three-dimensional space. Through various truncation operations, the
cubic honeycomb The cubic honeycomb or cubic cellulation is the only proper regular space-filling tessellation (or honeycomb) in Euclidean 3-space made up of cubic cells. It has 4 cubes around every edge, and 8 cubes around each vertex. Its vertex figure is a r ...
generates eight other convex uniform honeycombs under the group _3. The
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 ...
, with eight
equilateral 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 oth ...
s as
faces The face is the front of an animal's head that features the eyes, nose and mouth, and through which animals express many of their emotions. The face is crucial for human identity, and damage such as scarring or developmental deformities may affe ...
, is the
dual polyhedron In geometry, every polyhedron is associated with a second dual structure, where the vertices of one correspond to the faces of the other, and the edges between pairs of vertices of one correspond to the edges between pairs of faces of the oth ...
to the cube and one of eight convex deltahedra. The stella octangula, or ''eight-pointed star'', is the only
stellation In geometry, stellation is the process of extending a polygon in two dimensions, polyhedron in three dimensions, or, in general, a polytope in ''n'' dimensions to form a new figure. Starting with an original figure, the process extends specif ...
with
octahedral symmetry A regular octahedron has 24 rotational (or orientation-preserving) symmetries, and 48 symmetries altogether. These include transformations that combine a reflection and a rotation. A cube has the same set of symmetries, since it is the polyhedr ...
. It has eight triangular faces alongside eight vertices that form a cubic
faceting Stella octangula as a faceting of the cube In geometry, faceting (also spelled facetting) is the process of removing parts of a polygon, polyhedron or polytope, without creating any new vertices. New edges of a faceted polyhedron may be ...
, composed of two self-dual
tetrahedra 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 ...
that makes it the simplest of five regular compound polyhedra. The
cuboctahedron A cuboctahedron is a polyhedron with 8 triangular faces and 6 square faces. A cuboctahedron has 12 identical vertices, with 2 triangles and 2 squares meeting at each, and 24 identical edges, each separating a triangle from a square. As such, it ...
, on the other hand, is a rectified cube or rectified octahedron, and one of only two convex
quasiregular polyhedra In geometry, a quasiregular polyhedron is a uniform polyhedron that has exactly two kinds of regular faces, which alternate around each vertex. They are vertex-transitive and edge-transitive, hence a step closer to regular polyhedra than the sem ...
. It contains eight equilateral triangular faces alongside six squares, whose first
stellation In geometry, stellation is the process of extending a polygon in two dimensions, polyhedron in three dimensions, or, in general, a polytope in ''n'' dimensions to form a new figure. Starting with an original figure, the process extends specif ...
is the cube-octahedron compound. The
hexagonal prism In geometry, the hexagonal prism is a prism with hexagonal base. Prisms are polyhedrons; this polyhedron has 8 faces, 18 edges, and 12 vertices.. Since it has 8 faces, it is an octahedron. However, the term ''octahedron'' is primarily used ...
, which classifies as an irregular octahedron that is a
parallelohedron In geometry, a parallelohedron is a polyhedron that can be translated without rotations in 3-dimensional Euclidean space to fill space with a honeycomb in which all copies of the polyhedron meet face-to-face. There are five types of parallelohedr ...
, like the cube, is able to
tessellate A tessellation or tiling is the covering of a surface, often a plane, using one or more geometric shapes, called ''tiles'', with no overlaps and no gaps. In mathematics, tessellation can be generalized to higher dimensions and a variety of ...
space as a three-dimensional analogue of the
hexagon In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A '' regular hexagon'' has ...
. The gyrobifastigium, with four square faces and four triangular faces, is the only
Johnson solid In geometry, a Johnson solid is a strictly convex polyhedron each face of which is a regular polygon. There is no requirement that each face must be the same polygon, or that the same polygons join around each vertex. An example of a Johnso ...
that is able to tessellate space, while the
truncated octahedron In geometry, the truncated octahedron is the Archimedean solid that arises from a regular octahedron by removing six pyramids, one at each of the octahedron's vertices. The truncated octahedron has 14 faces (8 regular hexagons and 6 squares), 36 ...
, also a parallelohedron, is the permutohedron of order four, with eight hexagonal faces alongside six squares that is likewise the only
Archimedean solid In geometry, an Archimedean solid is one of the 13 solids first enumerated by Archimedes. They are the convex uniform polyhedra composed of regular polygons meeting in identical vertices, excluding the five Platonic solids (which are compose ...
that can generate a
honeycomb A honeycomb is a mass of hexagonal prismatic wax cells built by honey bees in their nests to contain their larvae and stores of honey and pollen. Beekeepers may remove the entire honeycomb to harvest honey. Honey bees consume about of honey ...
on its own.
Vertex-transitive In geometry, a polytope (e.g. a polygon or polyhedron) or a tiling is isogonal or vertex-transitive if all its vertices are equivalent under the symmetries of the figure. This implies that each vertex is surrounded by the same kinds of fa ...
semiregular polytope In geometry, by Thorold Gosset's definition a semiregular polytope is usually taken to be a polytope that is vertex-transitive and has all its facets being regular polytopes. E.L. Elte compiled a longer list in 1912 as ''The Semiregular Polyt ...
s whose
facets A facet is a flat surface of a geometric shape, e.g., of a cut gemstone. Facet may also refer to: Arts, entertainment, and media * ''Facets'' (album), an album by Jim Croce * ''Facets'', a 1980 album by jazz pianist Monty Alexander and his tri ...
are ''finite'' exist up through the 8th dimension. In the
third dimension Three-dimensional space (also: 3D space, 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called ''parameters'') are required to determine the position of an element (i.e., point). This is the informal ...
, they include the Archimedean solids and the infinite family of uniform
prisms Prism usually refers to: * Prism (optics), a transparent optical component with flat surfaces that refract light * Prism (geometry), a kind of polyhedron Prism may also refer to: Science and mathematics * Prism (geology), a type of sedimentar ...
and
antiprism In geometry, an antiprism or is a polyhedron composed of two parallel direct copies (not mirror images) of an polygon, connected by an alternating band of triangles. They are represented by the Conway notation . Antiprisms are a subclass o ...
s, while in the fourth dimension, only the
rectified 5-cell In four-dimensional geometry, the rectified 5-cell is a uniform 4-polytope composed of 5 regular tetrahedral and 5 regular octahedral cells. Each edge has one tetrahedron and two octahedra. Each vertex has two tetrahedra and three octahedra. In t ...
, the
rectified 600-cell In geometry, the rectified 600-cell or rectified hexacosichoron is a convex uniform 4-polytope composed of 600 regular octahedra and 120 icosahedra cells. Each edge has two octahedra and one icosahedron. Each vertex has five octahedra and two icos ...
, and the
snub 24-cell In geometry, the snub 24-cell or snub disicositetrachoron is a convex uniform 4-polytope composed of 120 regular tetrahedral and 24 icosahedral cells. Five tetrahedra and three icosahedra meet at each vertex. In total it has 480 triangular face ...
are semiregular polytopes. For dimensions
five 5 is a number, numeral, and glyph. 5, five or number 5 may also refer to: * AD 5, the fifth year of the AD era * 5 BC, the fifth year before the AD era Literature * ''5'' (visual novel), a 2008 visual novel by Ram * ''5'' (comics), an awa ...
through eight, the
demipenteract In five-dimensional geometry, a demipenteract or 5-demicube is a semiregular 5-polytope, constructed from a ''5-hypercube'' ( penteract) with alternated vertices removed. It was discovered by Thorold Gosset. Since it was the only semiregular ...
and the k21 polytopes 221, 321, and 421 are the only semiregular ( Gosset) polytopes. Collectively, the k21 family of polytopes contains eight figures that are rooted in the
triangular prism In geometry, a triangular prism is a three-sided prism; it is a polyhedron made of a triangular base, a translated copy, and 3 faces joining corresponding sides. A right triangular prism has rectangular sides, otherwise it is ''oblique''. A ...
, which is the simplest semiregular polytope that is made of three cubes and two equilateral triangles. It also includes one of only three semiregular Euclidean honeycombs: the
affine Affine may describe any of various topics concerned with connections or affinities. It may refer to: * Affine, a relative by marriage in law and anthropology * Affine cipher, a special case of the more general substitution cipher * Affine comb ...
521 honeycomb that represents the arrangement of vertices of the eight-dimensional \mathrm E_ lattice, and made of 421
facets A facet is a flat surface of a geometric shape, e.g., of a cut gemstone. Facet may also refer to: Arts, entertainment, and media * ''Facets'' (album), an album by Jim Croce * ''Facets'', a 1980 album by jazz pianist Monty Alexander and his tri ...
. The culminating figure is the ninth-dimensional 621 honeycomb, which is the only affine semiregular
paracompact In mathematics, a paracompact space is a topological space in which every open cover has an open refinement that is locally finite. These spaces were introduced by . Every compact space is paracompact. Every paracompact Hausdorff space is normal ...
hyperbolic Hyperbolic is an adjective describing something that resembles or pertains to a hyperbola (a curve), to hyperbole (an overstatement or exaggeration), or to hyperbolic geometry. The following phenomena are described as ''hyperbolic'' because they ...
honeycomb with infinite facets and
vertex figure In geometry, a vertex figure, broadly speaking, is the figure exposed when a corner of a polyhedron or polytope is sliced off. Definitions Take some corner or vertex of a polyhedron. Mark a point somewhere along each connected edge. Draw line ...
s in the k21 family. There are no other finite semiregular polytopes or honeycombs in dimensions ''n'' > 8. Sphenic numbers always have exactly eight divisors. The number 8 is involved with a number of interesting mathematical phenomena related to the notion of
Bott periodicity In mathematics, the Bott periodicity theorem describes a periodicity in the homotopy groups of classical groups, discovered by , which proved to be of foundational significance for much further research, in particular in K-theory of stable comp ...
. If O(\infty) is the direct limit of the inclusions of real orthogonal groups O(1)\hookrightarrow O(2)\hookrightarrow\ldots\hookrightarrow O(k)\hookrightarrow\ldots, the following holds: :\pi_(O(\infty))\cong\pi_(O(\infty)). Clifford algebras also display a periodicity of 8. For example, the algebra ''Cl''(''p'' + 8,''q'') is isomorphic to the algebra of 16 by 16 matrices with entries in ''Cl''(''p'',''q''). We also see a period of 8 in the
K-theory In mathematics, K-theory is, roughly speaking, the study of a ring generated by vector bundles over a topological space or scheme. In algebraic topology, it is a cohomology theory known as topological K-theory. In algebra and algebraic geometr ...
of spheres and in the
representation theory Representation theory is a branch of mathematics that studies abstract algebraic structures by ''representing'' their elements as linear transformations of vector spaces, and studies modules over these abstract algebraic structures. In essen ...
of the rotation groups, the latter giving rise to the 8 by 8
spinor In geometry and physics, spinors are elements of a complex vector space that can be associated with Euclidean space. Like geometric vectors and more general tensors, spinors transform linearly when the Euclidean space is subjected to a sligh ...
ial chessboard. All of these properties are closely related to the properties of the
octonion In mathematics, the octonions are a normed division algebra over the real numbers, a kind of hypercomplex number system. The octonions are usually represented by the capital letter O, using boldface or blackboard bold \mathbb O. Octonions hav ...
s. The
spin group In mathematics the spin group Spin(''n'') page 15 is the double cover of the special orthogonal group , such that there exists a short exact sequence of Lie groups (when ) :1 \to \mathrm_2 \to \operatorname(n) \to \operatorname(n) \to 1. As a ...
Spin(8) is the unique such group that exhibits the phenomenon of triality. The lowest-dimensional even unimodular lattice is the 8-dimensional \mathrm E_ lattice. Even positive definite unimodular lattices exist only in dimensions divisible by 8. A figure 8 is the common name of a
geometric Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is ca ...
shape A shape or figure is a graphical representation of an object or its external boundary, outline, or external surface, as opposed to other properties such as color, texture, or material type. A plane shape or plane figure is constrained to lie ...
, often used in the context of sports, such as skating. Figure-eight turns of a rope or cable around a cleat, pin, or bitt are used to belay something.


List of basic calculations


Etymology

English ''eight'', from Old English ''eahta, æhta'',
Proto-Germanic Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the reconstructed proto-language of the Germanic branch of the Indo-European languages. Proto-Germanic eventually developed from pre-Proto-Germanic into three Germanic br ...
''*ahto'' is a direct continuation of
Proto-Indo-European Proto-Indo-European (PIE) is the reconstructed common ancestor of the Indo-European language family. Its proposed features have been derived by linguistic reconstruction from documented Indo-European languages. No direct record of Proto-Indo ...
'' *oḱtṓ(w)-'', and as such cognate with Greek and Latin ''octo-'', both of which stems are reflected by the English prefix oct(o)-, as in the ordinal adjective ''octaval'' or ''octavary'', the distributive adjective is '' octonary''. The adjective ''octuple'' (Latin ''octu-plus'') may also be used as a noun, meaning "a set of eight items"; the diminutive ''
octuplet A multiple birth is the culmination of one multiple pregnancy, wherein the mother gives birth to two or more babies. A term most applicable to vertebrate species, multiple births occur in most kinds of mammals, with varying frequencies. Such bir ...
'' is mostly used to refer to eight siblings delivered in one birth. The Semitic numeral is based on a root ''*θmn-'', whence Akkadian ''smn-'', Arabic ''ṯmn-'', Hebrew ''šmn-'' etc. The
Chinese numeral Chinese numerals are words and characters used to denote numbers in Chinese. Today, speakers of Chinese use three written numeral systems: the system of Arabic numerals used worldwide, and two indigenous systems. The more familiar indigenous ...
, written ( Mandarin: ''bā'';
Cantonese Cantonese ( zh, t=廣東話, s=广东话, first=t, cy=Gwóngdūng wá) is a language within the Chinese (Sinitic) branch of the Sino-Tibetan languages originating from the city of Guangzhou (historically known as Canton) and its surrounding a ...
: ''baat''), is from
Old Chinese Old Chinese, also called Archaic Chinese in older works, is the oldest attested stage of Chinese, and the ancestor of all modern varieties of Chinese. The earliest examples of Chinese are divinatory inscriptions on oracle bones from around 12 ...
''*priāt-'', ultimately from Sino-Tibetan ''b-r-gyat'' or ''b-g-ryat'' which also yielded Tibetan '' brgyat''. It has been argued that, as the
cardinal number In mathematics, cardinal numbers, or cardinals for short, are a generalization of the natural numbers used to measure the cardinality (size) of sets. The cardinality of a finite set is a natural number: the number of elements in the set. ...
is the highest number of items that can universally be cognitively processed as a single set, the etymology of the numeral ''eight'' might be the first to be considered composite, either as "twice four" or as "two short of ten", or similar. The Turkic words for "eight" are from a Proto-Turkic stem ''*sekiz'', which has been suggested as originating as a negation of ''eki'' "two", as in "without two fingers" (i.e., "two short of ten; two fingers are not being held up"); this same principle is found in Finnic '' *kakte-ksa'', which conveys a meaning of "two before (ten)". The Proto-Indo-European reconstruction '' *oḱtṓ(w)-'' itself has been argued as representing an old dual, which would correspond to an original meaning of "twice four". Proponents of this "quaternary hypothesis" adduce the numeral ', which might be built on the stem ''new-'', meaning "new" (indicating the beginning of a "new set of numerals" after having counted to eight).


Evolution of the Arabic digit

The modern digit 8, like all modern
Arabic numerals Arabic numerals are the ten numerical digits: , , , , , , , , and . They are the most commonly used symbols to write decimal numbers. They are also used for writing numbers in other systems such as octal, and for writing identifiers such a ...
other than zero, originates with the
Brahmi numerals The Brahmi numerals are a numeral system attested from the 3rd century BCE (somewhat later in the case of most of the tens). They are a non positional decimal system. They are the direct graphic ancestors of the modern Hindu–Arabic numeral ...
. The Brahmi digit for ''eight'' by the 1st century was written in one stroke as a curve └┐ looking like an uppercase H with the bottom half of the left line and the upper half of the right line removed. However, the digit for eight used in India in the early centuries of the Common Era developed considerable graphic variation, and in some cases took the shape of a single wedge, which was adopted into the Perso-Arabic tradition as ٨ (and also gave rise to the later Devanagari form ); the alternative curved glyph also existed as a variant in Perso-Arabic tradition, where it came to look similar to our digit 5. The digits as used in
Al-Andalus Al-Andalus translit. ; an, al-Andalus; ast, al-Ándalus; eu, al-Andalus; ber, ⴰⵏⴷⴰⵍⵓⵙ, label= Berber, translit=Andalus; ca, al-Àndalus; gl, al-Andalus; oc, Al Andalús; pt, al-Ândalus; es, al-Ándalus () was the M ...
by the 10th century were a distinctive western variant of the glyphs used in the Arabic-speaking world, known as ''ghubār'' numerals (''ghubār'' translating to " sand table"). In these digits, the line of the ''5''-like glyph used in Indian manuscripts for eight came to be formed in ghubār as a closed loop, which was the ''8''-shape that became adopted into European use in the 10th century. Just as in most modern
typeface A typeface (or font family) is the design of lettering that can include variations in size, weight (e.g. bold), slope (e.g. italic), width (e.g. condensed), and so on. Each of these variations of the typeface is a font. There are thousands o ...
s, in typefaces with
text figures Text figures (also known as non-lining, lowercase, old style, ranging, hanging, medieval, billing, or antique figures or numerals) are numerals designed with varying heights in a fashion that resembles a typical line of running text, hence the ...
the character for the digit 8 usually has an ascender, as, for example, in . The
infinity symbol The infinity symbol (\infty) is a mathematical symbol representing the concept of infinity. This symbol is also called a lemniscate, after the lemniscate curves of a similar shape studied in algebraic geometry, or "lazy eight", in the terminol ...
∞, described as a "sideways figure eight", is unrelated to the digit 8 in origin; it is first used (in the mathematical meaning "infinity") in the 17th century, and it may be derived from the
Roman numeral Roman numerals are a numeral system that originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. Numbers are written with combinations of letters from the Latin alphabet, ea ...
for "one thousand" CIƆ, or alternatively from the final Greek letter, ω.


In science


Physics

* In nuclear physics, the second magic number. * In
particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...
, the eightfold way is used to classify sub-atomic particles. * In
statistical mechanics In physics, statistical mechanics is a mathematical framework that applies statistical methods and probability theory to large assemblies of microscopic entities. It does not assume or postulate any natural laws, but explains the macroscopic b ...
, the eight-vertex model has 8 possible configurations of arrows at each vertex.


Astronomy

*
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 ...
M8, a magnitude 5.0
nebula A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...
in the
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the earliest constellation ...
of Sagittarius. * The
New General Catalogue The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and ...
br>object
NGC 8 NGC 8 is an asterism of two completely unrelated stars (spectral types K6I and G4) in the constellation Pegasus, discovered on 29 September 1865 by Otto Wilhelm von Struve. It is approximately 2.7 arc minutes away from NGC 9. The two sta ...
, a double star in the constellation
Pegasus Pegasus ( grc-gre, Πήγασος, Pḗgasos; la, Pegasus, Pegasos) is one of the best known creatures in Greek mythology. He is a winged divine stallion usually depicted as pure white in color. He was sired by Poseidon, in his role as hor ...
. * Since the demotion of
Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the S ...
to a
dwarf planet A dwarf planet is a small planetary-mass object that is in direct orbit of the Sun, smaller than any of the eight classical planets but still a world in its own right. The prototypical dwarf planet is Pluto. The interest of dwarf planets to ...
on 24 August 2006, in our
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 ...
, eight of the bodies orbiting the Sun are considered to be
planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...
s.


Chemistry

* The
atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of ever ...
of
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
. * The most stable allotrope of a
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
molecule is made of eight sulfur atoms arranged in a rhombic form. * The maximum number of electrons that can occupy a valence shell. * The red pigment
lycopene Lycopene is an organic compound classified as a tetraterpene and a carotene. Lycopene (from the neo-Latin '' Lycopersicum'', the tomato species) is a bright red carotenoid hydrocarbon found in tomatoes and other red fruits and vegetables. Occu ...
consists of eight
isoprene Isoprene, or 2-methyl-1,3-butadiene, is a common volatile organic compound with the formula CH2=C(CH3)−CH=CH2. In its pure form it is a colorless volatile liquid. Isoprene is an unsaturated hydrocarbon. It is produced by many plants and animals ...
units.


Geology

* A
disphenoid In geometry, a disphenoid () is a tetrahedron whose four faces are congruent acute-angled triangles. It can also be described as a tetrahedron in which every two edges that are opposite each other have equal lengths. Other names for the same ...
crystal is bounded by eight scalene triangles arranged in pairs. A ditetragonal prism in the
tetragonal crystal system In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a squar ...
has eight similar faces whose alternate interfacial angles only are equal.


Biology

* All
spider Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...
s, and more generally all
arachnid Arachnida () is a class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegar ...
s, have eight legs.
Orb-weaver spider Orb-weaver spiders are members of the spider family (biology), family Araneidae. They are the most common group of builders of spiral wheel-shaped spider web, webs often found in gardens, fields, and forests. The English word "orb" can mean "circ ...
s of the cosmopolitan family Areneidae have eight similar eyes. * The
octopus An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, ...
and its cephalopod relatives in genus ''Argonauta'' have eight arms (tentacles). * Compound coelenterates of the subclass or order Alcyonaria have polyps with eight-branched tentacles and eight septa. * Sea anemones of genus '' Edwardsia'' have eight
mesenteries In zoology, a mesentery is a membrane inside the body cavity of an animal. The term identifies different structures in different phyla: in vertebrates it is a double fold of the peritoneum enclosing the intestines; in other organisms it forms com ...
. * Animals of phylum
Ctenophora Ctenophora (; ctenophore ; ) comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), and ...
swim by means of eight meridional bands of transverse ciliated plates, each plate representing a row of large modified cilia. * The eight-spotted forester (genus ''Alypia'', family
Zygaenidae The Zygaenidae moths are a family of Lepidoptera. The majority of zygaenids are tropical, but they are nevertheless quite well represented in temperate regions. Some of the 1000 or so species are commonly known as burnet or forester moths, oft ...
) is a diurnal moth having black wings with brilliant white spots. * The
ascus An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera o ...
in fungi of the class
Ascomycetes Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The defi ...
, following nuclear fusion, bears within it typically eight ascospores. * Herbs of genus ''
Coreopsis ''Coreopsis'' () is a genus of flowering plants in the family Asteraceae. Common names include calliopsis and tickseed, a name shared with various other plants. Description These plants range from in height. The flowers are usually yellow wi ...
'' (tickseed) have showy flower heads with involucral bracts in two distinct series of eight each. * In human adult dentition there are eight teeth in each quadrant. The eighth tooth is the so-called
wisdom tooth 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 ...
. * There are eight cervical nerves on each side in man and most mammals.


Psychology

* There are eight Jungian cognitive functions, according to the MBTI models by John Beebe and Linda Berens. *
Timothy Leary Timothy Francis Leary (October 22, 1920 – May 31, 1996) was an American psychologist and author known for his strong advocacy of psychedelic drugs. Evaluations of Leary are polarized, ranging from bold oracle to publicity hound. He was "a her ...
identified a hierarchy of eight levels of consciousness.


In technology

* A
byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...
is eight bits. * Many (mostly historic) computer architectures are eight-bit, among them the
Nintendo Entertainment System The Nintendo Entertainment System (NES) is an 8-bit third-generation home video game console produced by Nintendo. It was first released in Japan in 1983 as the commonly known as the The NES, a redesigned version, was released in America ...
. * Standard-8 and
Super-8 Super 8 mm film is a motion-picture film format released in 1965 by Eastman Kodak as an improvement over the older "Double" or "Regular" 8 mm home movie format. The film is nominally 8 mm wide, the same as older formatted 8& ...
are 8 mm
film formats A film format is a technical definition of a set of standard characteristics regarding image capture on photographic film for still images or film stock for filmmaking. It can also apply to projected film, either slides or movies. The primary ch ...
. * Video8, Hi8 and Digital8 are related
8 mm video format The 8mm video format refers informally to three related videocassette formats. These are the original Video8 ( analog recording) format and its improved successor Hi8 ( analog video and analog audio but with provision for digital audio), as wel ...
s. * On most phones, the 8 key is associated with the letters T, U, and V, but on the BlackBerry Pearl it is the key for B and N. * An eight may refer to an eight-cylinder engine or automobile. A
V8 engine A V8 engine is an eight-cylinder piston engine in which two banks of four cylinders share a common crankshaft and are arranged in a V configuration. The first V8 engine was produced by the French Antoinette company in 1904, developed and u ...
is an
internal combustion engine 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 co ...
with eight cylinders configured in two banks (rows) of four forming a "V" when seen from the end. * A
figure-eight knot The figure-eight knot or figure-of-eight knot is a type of stopper knot. It is very important in both sailing and rock climbing as a method of stopping ropes from running out of retaining devices. Like the overhand knot, which will jam under st ...
(so named for its configuration) is a kind of
stopper knot Stopper may refer to: * Bung, a plug used to stop the opening of a container ** Laboratory rubber stopper, a specific type of bung * Plug (sanitation), used to stop a drainage outlet * Defender (association football), in soccer (association foo ...
. * The number eight written in parentheses is the code for the musical note in
Windows Live Messenger MSN Messenger (also known colloquially simply as "Messenger"), later rebranded as Windows Live Messenger, was a cross-platform instant-messaging client developed by Microsoft. It connected to the Microsoft Messenger service and, in later versio ...
. * In a
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, bas ...
, when an 8 is illuminated, all the display bulbs are on.


In measurement

* The
SI prefix The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. ...
for 10008 is yotta (Y), and for its reciprocal, yocto (y). * In liquid measurement (
United States customary units United States customary units form a system of measurement units commonly used in the United States and U.S. territories since being standardized and adopted in 1832. The United States customary system (USCS or USC) developed from English uni ...
), there are eight
fluid ounce A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl., old forms ℥, fl ℥, f℥, ƒ ℥) is a unit of volume (also called ''capacity'') typically used for measuring liquids. The British Imperial, the United States customary, and the United ...
s in a
cup A cup is an open-top used to hold hot or cold liquids for pouring or drinking; while mainly used for drinking, it also can be used to store solids for pouring (e.g., sugar, flour, grains, salt). Cups may be made of glass, metal, china, cl ...
, eight
pint The pint (, ; symbol pt, sometimes abbreviated as ''p'') is a unit of volume or capacity in both the imperial and United States customary measurement systems. In both of those systems it is traditionally one eighth of a gallon. The British impe ...
s in a
gallon The gallon is a unit of volume in imperial units and United States customary units. Three different versions are in current use: *the imperial gallon (imp gal), defined as , which is or was used in the United Kingdom, Ireland, Canada, Aust ...
and eight
tablespoon A tablespoon (tbsp. , Tbsp. , Tb. , or T.) is a large spoon. In many English-speaking regions, the term now refers to a large spoon used for serving; however, in some regions, it is the largest type of spoon used for eating. By extension, the ter ...
fuls in a
gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they ar ...
. * There are eight
furlong A furlong is a measure of distance in imperial units and United States customary units equal to one eighth of a mile, equivalent to 660 feet, 220 yards, 40 rods, 10 chains or approximately 201 metres. It is now mostly confined to use in hor ...
s in a mile. * The clove, an old English unit of weight, was equal to eight pounds when measuring cheese. * An eight may be an article of clothing of the eighth
size Size in general is the magnitude or dimensions of a thing. More specifically, ''geometrical size'' (or ''spatial size'') can refer to linear dimensions ( length, width, height, diameter, perimeter), area, or volume. Size can also be me ...
. * Force eight is the first
wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ...
strength attributed to a
gale A gale is a strong wind; the word is typically used as a descriptor in nautical contexts. The U.S. National Weather Service defines a gale as sustained surface winds moving at a speed of between 34 and 47 knots (, or ).Beaufort scale The Beaufort scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale. History The scale was devised in 1805 by the Irish hydrographer Francis Beaufort ...
when announced on a
Shipping Forecast The Shipping Forecast is a BBC Radio broadcast of weather reports and forecasts for the seas around the coasts of the British Isles. It is produced by the Met Office and broadcast by BBC Radio 4 on behalf of the Maritime and Coastguard Agency. ...
.


In culture


Currency

* Sailors and civilians alike from the 1500s onward referred to evenly divided parts of the
Spanish dollar The Spanish dollar, also known as the piece of eight ( es, Real de a ocho, , , or ), is a silver coin of approximately diameter worth eight Spanish reales. It was minted in the Spanish Empire following a monetary reform in 1497 with content ...
as "pieces of eight", or "bits".


Architecture

* Various types of buildings are usually eight-sided (octagonal), such as single-roomed
gazebo A gazebo is a pavilion structure, sometimes octagonal or turret-shaped, often built in a park, garden or spacious public area. Some are used on occasions as bandstands. Etymology The etymology given by Oxford Dictionaries is "Mid 18th c ...
s and multi-roomed
pagoda A pagoda is an Asian tiered tower with multiple eaves common to Nepal, India, China, Japan, Korea, Myanmar, Vietnam, and other parts of Asia. Most pagodas were built to have a religious function, most often Buddhist but sometimes Taoist, ...
s (descended from stupas; see religion section below). * Eight caulicoles rise out of the leafage in a
Corinthian capital The Corinthian order (Greek: Κορινθιακός ρυθμός, Latin: ''Ordo Corinthius'') is the last developed of the three principal classical orders of Ancient Greek architecture and Roman architecture. The other two are the Doric order w ...
, ending in leaves that support the
volutes A volute is a spiral, scroll-like ornament that forms the basis of the Ionic order, found in the capital of the Ionic column. It was later incorporated into Corinthian order and Composite column capitals. Four are normally to be found on an Ion ...
.


In religion, folk belief and divination


Hinduism

* Also known as Ashtha, Aṣṭa, or Ashta in
Sanskrit Sanskrit (; attributively , ; nominally , , ) is a classical language belonging to the Indo-Aryan languages, Indo-Aryan branch of the Indo-European languages. It arose in South Asia after its predecessor languages had Trans-cultural diffusion ...
, it is the number of wealth and abundance. * The goddess of wealth and prosperity,
Lakshmi Lakshmi (; , sometimes spelled Laxmi, ), also known as Shri (, ), is one of the principal goddesses in Hinduism. She is the goddess of wealth, fortune, power, beauty, fertility and prosperity, and associated with '' Maya'' ("Illusion"). A ...
, has eight forms known as Ashta Lakshmi and worshipped as:
"''Maha-lakshmi, Dhana-lakshmi, Dhanya-lakshmi, Gaja-lakshmi,
Santana-lakshmi, Veera-lakshmi, Vijaya-lakshmi and Vidhya-lakshmi''" *There are eight ''nidhi'', or seats of wealth, according to
Hinduism Hinduism () is an Indian religion or '' dharma'', a religious and universal order or way of life by which followers abide. As a religion, it is the world's third-largest, with over 1.2–1.35 billion followers, or 15–16% of the global p ...
. *There are eight
guardians of the directions The Guardians of the Directions (Sanskrit: दिक्पाल, Dikpāla) are the deities who rule the specific directions of space according to Hinduism, Jainism and '' '' Buddhism—especially . As a group of eight deities, they are called ( ...
known as ''Astha-dikpalas''. *There are eight
Hindu Hindus (; ) are people who religiously adhere to Hinduism. Jeffery D. Long (2007), A Vision for Hinduism, IB Tauris, , pages 35–37 Historically, the term has also been used as a geographical, cultural, and later religious identifier for ...
monasteries established by the saint
Madhvacharya Madhvacharya (; ; CE 1199-1278 or CE 1238–1317), sometimes anglicised as Madhva Acharya, and also known as Purna Prajna () and Ānanda Tīrtha, was an Indian philosopher, theologian and the chief proponent of the '' Dvaita'' (dualism) sch ...
in
Udupi Udupi (alternate spelling Udipi; also known as Odipu) is a city in the Indian state of Karnataka. Udupi is situated about north of the educational, commercial and industrial hub of Mangalore and about west of state capital Bangalore by road. ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
popularly known as the '' Ashta Mathas of Udupi''.


Buddhism

* The
Dharmacakra The dharmachakra (Sanskrit: धर्मचक्र; Pali: ''dhammacakka'') or wheel of dharma is a widespread symbol used in Indian religions such as Hinduism, Jainism, and especially Buddhism.John C. Huntington, Dina Bangdel, ''The Circle o ...
, a
Buddhist Buddhism ( , ), also known as Buddha Dharma and Dharmavinaya (), is an Indian religion or philosophical tradition based on teachings attributed to the Buddha. It originated in northern India as a -movement in the 5th century BCE, and ...
symbol, has eight spokes. The Buddha's principal teaching—the
Four Noble Truths In Buddhism, the Four Noble Truths (Sanskrit: ; pi, cattāri ariyasaccāni; "The four Arya satyas") are "the truths of the Noble Ones", the truths or realities for the "spiritually worthy ones". Four Noble Truths: BUDDHIST PHILOSOPHY Encycl ...
—ramifies as the Noble Eightfold Path and the Buddha emphasizes the importance of the eight attainments or jhanas. * In Mahayana Buddhism, the branches of the Eightfold Path are embodied by the Eight Great Bodhisattvas: (Manjusri, Vajrapani, Avalokiteśvara, Maitreya, Ksitigarbha, Nivaranavishkambhi, Akasagarbha, and Samantabhadra (Bodhisattva), Samantabhadra). These are later (controversially) associated with the Eight Consciousnesses according to the
Yogacara Yogachara ( sa, योगाचार, IAST: '; literally "yoga practice"; "one whose practice is yoga") is an influential tradition of Buddhist philosophy and psychology emphasizing the study of cognition, perception, and consciousness through ...
school of thought: consciousness in the five senses, thought-consciousness, self-consciousness, and unconsciousness-"consciousness" or "store-house consciousness" (alaya-vijñana). The "irreversible" state of enlightenment, at which point a Bodhisattva goes on "autopilot", is the Eight Ground or ''bhūmi''. In general, "eight" seems to be an auspicious number for Buddhists, e.g., the "eight auspicious symbols" (the jewel-encrusted parasol; the goldfish (always shown as a pair, e.g., the glyph of Pisces); the self-replenishing amphora; the white ''kamala'' lotus-flower; the white conch; the eternal (Celtic-style, infinitely looping) knot; the banner of imperial victory; the eight-spoked wheel that guides the ship of state, or that symbolizes the Buddha's teaching). Similarly,
Buddha's birthday Buddha's Birthday (also known as Buddha Jayanti, also known as his day of enlightenment – Buddha Purnima, Buddha Pournami) is a Buddhist festival that is celebrated in most of East Asia and South Asia commemorating the birth of the Prince ...
falls on the 8th day of the 4th month of the
Chinese calendar The traditional Chinese calendar (also known as the Agricultural Calendar 曆; 农历; ''Nónglì''; 'farming calendar' Former Calendar 曆; 旧历; ''Jiùlì'' Traditional Calendar 曆; 老历; ''Lǎolì'', is a lunisolar calendar ...
.


Judaism

* The religious rite of
brit milah The ''brit milah'' ( he, בְּרִית מִילָה ''bərīṯ mīlā'', ; Ashkenazi pronunciation: , " covenant of circumcision"; Yiddish pronunciation: ''bris'' ) is the ceremony of circumcision in Judaism. According to the Book of Genes ...
(commonly known as
circumcision Circumcision is a procedure that removes the foreskin from the human penis. In the most common form of the operation, the foreskin is extended with forceps, then a circumcision device may be placed, after which the foreskin is excised. Top ...
) is held on a baby boy's eighth day of life. * Hanukkah is an eight-day Jewish holiday that starts on the 25th day of Kislev. * Shemini Atzeret (Hebrew language, Hebrew: "Eighth Day of Assembly") is a one-day Jewish holiday immediately following the seven-day holiday of Sukkot.


Christianity

* The spiritual The eighth day (Christian), Eighth Day, because the number 7 refers to the days of the week (which repeat themselves). * The number of Beatitudes. * wikisource:Bible (King James)/1 Peter#3:20, 1 Peter 3:20 states that there were eight people on Noah's Ark. * The Antichrist is the eighth king in the Book of Revelation.


Islam

* In Islam, eight is the number of angels carrying the Throne of God, throne of Allah in heaven. * The number of gates of heaven


Taoism

* Ba Gua * Ba Xian * baduanjin, Ba Duan Jin


Other

* In Wicca, there are eight Sabbats, festivals, seasons, or spokes in the Wheel of the Year. * In Ancient Egyptian mythology, the Ogdoad (Egyptian), Ogdoad represents the Ancient Egyptian creation myths, eight primordial deities of creation. * In Scientology there are eight dynamics of existence. * There is also the Ogdoad (Gnosticism), Ogdoad in Gnosticism.


As a lucky number

* The number eight is considered to be a Numbers in Chinese culture, lucky number in Chinese and other Asian cultures. Eight (; Chinese numerals#Numeral characters, accounting ; pinyin ''bā'') is considered a Numbers in Chinese culture#Eight, lucky number in Chinese culture because it sounds like the word meaning to generate wealth (; Pinyin: ''fā''). Property with the number 8 may be valued greatly by Chinese. For example, a Hong Kong Vehicle registration plate, number plate with the number 8 was sold for $640,000. The opening ceremony of the 2008 Summer Olympics, Summer Olympics in Beijing started at 8 seconds and 8 minutes past 8 pm (local time) on 8 August 2008. * In Pythagorean numerology (a pseudoscience) the number 8 represents victory, prosperity and overcoming. * is also considered a lucky number in Japan, but the reason is different from that in Chinese culture. Eight gives an idea of growing prosperous, because the letter () broadens gradually. * The Japanese thought of as a holy number in the ancient times. The reason is less well-understood, but it is thought that it is related to the fact they used eight to express large numbers vaguely such as (literally, eightfold and twentyfold), (literally, eight clouds), (literally, eight millions of Gods), etc. It is also guessed that the ancient Japanese gave importance to pairs, so some researchers guess twice as , which is also guessed to be a holy number in those times because it indicates the world (north, south, east, and west) might be considered a very holy number. * In numerology, 8 is the number of building, and in some theories, also the number of destruction.


In astrology

* In astrology, Scorpius, Scorpio is the 8th astrological sign of the Zodiac. * In the Middle Ages, 8 was the number of "unmoving" stars in the sky, and symbolized the perfection of incoming planetary energy.


In music and dance

* A note played for one-eighth the duration of a whole note is called an eighth note, or quaver. * An octave, the interval between two musical notes with the same letter name (where one has double the frequency of the other), is so called because there are eight notes between the two on a standard major or minor diatonic scale, including the notes themselves and without chromatic deviation. The ecclesiastical musical mode, modes are ascending diatonic musical scales of eight notes or tones comprising an octave. * There are eight notes in the octatonic scale. * There are eight musicians in a double quartet or an octet (music), octet. Both terms may also refer to a musical composition for eight voices or instruments. * Caledonians is a square dance for eight, resembling the quadrille. * Albums with the number eight in their title include ''8'' by the Swedish band Arvingarna, ''8 (Incubus album), 8'' by the American rock band Incubus (band), Incubus, ''The Meaning of 8'' by Minnesota indie rock band Cloud Cult and ''8ight'' by Anglo-American singer-songwriter Beatie Wolfe. * Dream Theater's eighth album ''Octavarium (album), Octavarium'' contains many different references to the number 8, including the number of songs and various aspects of the music and cover artwork. * "Eight maids a-milking" is the gift on the eighth day of Christmas in the carol "The Twelve Days of Christmas (song), The Twelve Days of Christmas". * The 8-track tape, 8-track cartridge is a musical recording format. * "#8" is the stage name of Slipknot (band), Slipknot vocalist Corey Taylor. * "Too Many Eights" is a song by Athens, Georgia's Supercluster (band), Supercluster. * Eight Seconds, a Canadian musical group popular in the 1980s with their most notable song "Kiss You (When It's Dangerous)". * "Eight Days a Week (song), Eight Days a Week" is a #1 single for the music group The Beatles. * Figure 8 (album), ''Figure 8'' is the fifth studio album by singer-songwriter Elliott Smith, released in the year 2000, an album released by Julia Darling in 1999, and an album released by Outasight in 2011. * Ming Hao from the k-pop group Seventeen (South Korean band)#Performance team, Seventeen goes by the name "The8". * "8 (circle)" is the eighth song on the album ''22, A Million'' by the American band Bon Iver. * "8" is the eighth song on the album ''When We All Fall Asleep, Where Do We Go?'' by Billie Eilish.


In film and television

* ''8 Guys'' is a 2003 short film written and directed by Dane Cook. * ''8 Man'' (or ''Eightman''): 1963 Japanese manga and anime superhero. * 8 Mile (film), ''8 Mile'' is a 2002 film directed by Curtis Hanson. * 8mm (film), ''8 mm'' is a 1999 film directed by Joel Schumacher. * ''8 Women'' (Original French title: ) is a 2001 film directed by François Ozon. * ''Eight Below'' is a 2006 film directed by Frank Marshall (film producer), Frank Marshall. * ''Eight Legged Freaks'' is a 2002 film directed by Ellory Elkayem. * ''Eight Men Out'' is a 1988 film directed by John Sayles. * ''Jennifer Eight'', also known as ''Jennifer 8'', is a 1992 film written and directed by Bruce Robinson. * ''Eight Is Enough'' is an American television comedy-drama series. * In ''Stargate SG-1'' and ''Stargate Atlantis'', dialing an 8-chevron address will open a wormhole to another galaxy. * ''The Hateful Eight'' is a 2015 American western mystery film written and directed by Quentin Tarantino. * ''Kate Plus 8'' is an American reality television show.


In sports and other games

* Eight-ball pool (cue sports), pool is played with a cue ball and 15 numbered balls, the black ball numbered 8 being the middle and most important one, as the winner is the player or side that legally pockets it after first pocketing its numerical group of 7 object balls (for other meanings see ''Eight ball (disambiguation)''). * In chess, each side has eight pawns and the board is made of 64 squares arranged in an eight by eight lattice. The eight queens puzzle is a challenge to arrange eight queens on the board so that none can capture any of the others. * In the game of eights or Crazy Eights, each successive player must play a card either of the same suit or of the same rank as that played by the preceding player, or may play an eight and call for any suit. The object is to get rid of all one's cards first. * In association football, the number 8 has historically been the number of the Central Midfielder. * In Australian rules football, the top eight teams at the end of the Australian Football League regular season qualify for the AFL finals series, finals series (i.e. playoffs). * In baseball: ** The center fielder is designated as number 8 for scorekeeping purposes. ** The College World Series, the final phase of the NCAA Division I Baseball Championship, NCAA Division I tournament, features eight teams. * In rugby union, the only position without a proper name is the Number eight (rugby union), Number 8, a forward position. * In rugby league: ** Most competitions (though not the Super League, which uses static squad numbering) use a position-based player numbering system in which one of the two starting props wears the number 8. ** The Australia-based National Rugby League has its own 8-team finals series, similar but not identical in structure to that of the Australian Football League. * In Rowing (sport), rowing, an "eight" refers to a sweep-oar racing boat with a crew of eight rowers plus a coxswain. * In the 2008 Summer Olympics, 2008 Games of the XXIX Olympiad held in Beijing, the official opening was on 08/08/08 at 8:08:08 p.m. China Standard Time, CST. * In Rock Climbing, climbers frequently use the Figure-eight knot, Figure Eight knot to tie into their harnesses.


In foods

* Nestlé sells a brand of chocolates filled with peppermint-flavoured cream called After Eight, referring to the time 8 p.m. * There are eight vegetables in V8 (beverage), V8 juice.


In literature

* Eights may refer to octosyllable, octosyllabic, usually Choliamb, iambic, Meter (poetry), lines of verse. * The drott-kvaett, an Old Icelandic verse, consisted of a stanza of eight regular lines. * In Terry Pratchett's ''Discworld'' series, eight is a magical number and is considered taboo. Eight is not safe to be said by wizards on the Discworld (world), Discworld and is the number of Bel-Shamharoth. Also, there are eight days in a Disc week and eight colours in a Disc spectrum, the eighth one being octarine. * Lewis Carroll's poem ''The Hunting of the Snark'' has 8 "fits" (cantos), which is noted in the full name "The Hunting of the Snark – ''An Agony, in Eight Fits''." * Eight apparitions appear to Macbeth (character), Macbeth in Act 4 scene 1 of Shakespeare's ''Macbeth'' as representations of the eight descendants of Banquo.


In slang

* An "eighth" is a common measurement of cannabis (drug), marijuana, meaning an eighth of an ounce. It is also a common unit of sale for psilocybin mushrooms. * Avril Lavigne's song "Sk8er Boi" uses this convention in the title. * "Section 8" is common U.S. slang for "crazy", based on the United States armed forces, U.S. military's Section 8 (military), Section 8 discharge for Mental disorder, mentally unfit personnel. * The Section 8 (housing), Housing Choice Voucher Program, operated by the United States Department of Housing and Urban Development, is commonly referred to as the Section 8 program, as this was the original section of the Act which instituted the program. * In Colombia and Venezuela, "volverse un ocho" (meaning to tie oneself in a figure 8) refers to getting in trouble or contradicting oneself. * In China, "8" is used in chat speak as a term for parting. This is due to the closeness in pronunciation of "8" (bā) and the English word "bye".


See also

* The Magical Number Seven, Plus or Minus Two *List of highways numbered 8


References


External links


The Octonions
John C. Baez {{DEFAULTSORT:8 (Number) Integers 8 (number)