1 (one, also called unit, and unity) is a

^{''x''}) always equals 1, its

The Number 1

The Positive Integer 1

{{DEFAULTSORT:1 (Number) Integers

number
A number is a mathematical object
A mathematical object is an abstract concept arising in mathematics.
In the usual language of mathematics, an ''object'' is anything that has been (or could be) formally defined, and with which one may do deduct ...

and a numerical digit
A numerical digit (often shortened to just digit) is a single symbol used alone (such as "2") or in combinations (such as "25"), to represent number
A number is a mathematical object
A mathematical object is an abstract concept arising in mat ...

used to represent that number in numeral
A numeral is a figure, symbol, or group of figures or symbols denoting a number. It may refer to:
* Numeral system used in mathematics
* Numeral (linguistics), a part of speech denoting numbers (e.g. ''one'' and ''first'' in English)
* Numerical di ...

s. It represents a single entity, the unit
Unit may refer to:
Arts and entertainment
* UNIT
Unit may refer to:
Arts and entertainment
* UNIT, a fictional military organization in the science fiction television series ''Doctor Who''
* Unit of action, a discrete piece of action (or beat) in ...

of counting
Counting is the process of determining the number
A number is a mathematical object
A mathematical object is an abstract concept arising in mathematics.
In the usual language of mathematics, an ''object'' is anything that has been (or could be) ...

or measurement
Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. The scope and application of measurement are dependent on the context and discipline. In natural science
Natur ...

. For example, a line segment
250px, The geometric definition of a closed line segment: the intersection of all points at or to the right of ''A'' with all points at or to the left of ''B''
In geometry
Geometry (from the grc, γεωμετρία; ''wikt:γῆ, geo-'' ...

of ''unit length'' is a line segment of length
Length is a measure of distance
Distance is a numerical measurement
'
Measurement is the number, numerical quantification (science), quantification of the variable and attribute (research), attributes of an object or event, which can be us ...

1. In conventions of sign where zero is considered neither positive nor negative, 1 is the first and smallest positive integer
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). ...

. It is also sometimes considered the first of the infinite sequence
In mathematics
Mathematics (from Greek: ) includes the study of such topics as numbers ( and ), formulas and related structures (), shapes and spaces in which they are contained (), and quantities and their changes ( and ). There is no gene ...

of natural number
In mathematics, the natural numbers are those numbers used for counting (as in "there are ''six'' coins on the table") and total order, ordering (as in "this is the ''third'' largest city in the country"). In common mathematical terminology, w ...

s, followed by , although by other definitions 1 is the second natural number, following .
The fundamental mathematical property of 1 is to be a multiplicative identity
In mathematics, an identity element, or neutral element, is a special type of element of a set with respect to a binary operation on that set, which leaves any element of the set unchanged when combined with it. This concept is used in algebraic s ...

, meaning that any number multiplied by 1 returns that number. Most if not all properties of 1 can be deduced from this. In advanced mathematics, a multiplicative identity is often denoted 1, even if it is not a number. 1 is by convention not considered a prime number
A prime number (or a prime) is a natural number greater than 1 that is not a Product (mathematics), 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 ...

; although universal today, this was a matter of some controversy until the mid-20th century.
Etymology

The word ''one'' can be used as a noun, an adjective and a pronoun. It comes from the English word ''an'', which comes from the Proto-Germanic root . The Proto-Germanic root comes from the Proto-Indo-European root ''*oi-no-''. Compare the Proto-Germanic root toOld Frisian
Old Frisian was a West Germanic language spoken between the 8th and 16th centuries in the area between the Rhine
), Surselva
Surselva Region is one of the eleven administrative districts
Administrative division, administrative unitArticl ...

''an'', Gothic
Gothic or Gothics may refer to:
People and languages
*Goths or Gothic people, the ethnonym of a group of East Germanic tribes
**Gothic language, an extinct East Germanic language spoken by the Goths
**Crimean Gothic, the Gothic language spoken by ...

''ains'', Danish
Danish may refer to:
* Something of, from, or related to the country of Denmark
* A national or citizen of Denmark, also called a "Dane", see Demographics of Denmark
* Danish people or Danes, people with a Danish ancestral or ethnic identity
* Danis ...

''en'', Dutch
Dutch commonly refers to:
* Something of, from, or related to the Netherlands
* Dutch people ()
* Dutch language ()
*Dutch language , spoken in Belgium (also referred as ''flemish'')
Dutch may also refer to:"
Castle
* Dutch Castle
Places
* ...

''een'', German
German(s) may refer to:
Common uses
* of or related to Germany
* Germans, Germanic ethnic group, citizens of Germany or people of German ancestry
* For citizens of Germany, see also German nationality law
* German language
The German la ...

''eins'' and Old Norse
Old Norse, Old Nordic, or Old Scandinavian is a stage of development of North Germanic dialects before their final divergence into separate Nordic languages. Old Norse was spoken by inhabitants of Scandinavia
Scandinavia; : ''Skades ...

''einn''.
Compare the Proto-Indo-European root ''*oi-no-'' (which means "one, single") to Greek#REDIRECT Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece
Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...

''oinos'' (which means "ace" on dice), Latin
Latin (, or , ) is a classical language
A classical language is a language
A language is a structured system of communication
Communication (from Latin ''communicare'', meaning "to share" or "to be in relation with") is "an appa ...

''unus'' (one), Old Persian
Old Persian is one of the two directly attested Old Iranian languages
The Iranian or Iranic languages are a branch of the Indo-Iranian languagesIndo-Iranian may refer to:
* Indo-Iranian languages
* Indo-Iranians, the various peoples speaking ...

, Old Church Slavonic
Old Church Slavonic or Old Slavonic (, ) was the first Slavic literary language.
Historians credit the 9th-century Byzantine missionaries Saints Cyril and Methodius with standardizing the language and using it in translating the Bible
...

''-inu'' and ''ino-'', Lithuanian
Lithuanian may refer to:
* Lithuanians
Lithuanians ( lt, lietuviai, singular ''lietuvis/lietuvė'') are a Balts, Baltic ethnic group. They are native to Lithuania, where they number around 2,561,300 people. Another million or more make up the Lith ...

''vienas'', Old Irish
Old Irish (''Goídelc''; ga, Sean-Ghaeilge; gd, Seann Ghàidhlig; gv, Shenn Yernish or ; Old Irish: ᚌᚑᚔᚇᚓᚂᚉ), sometimes called Old Gaelic, is the oldest form of the Goidelic
The Goidelic or Gaelic languages ( ga, teangacha ...

''oin'' and Breton
Breton most often refers to:
*anything associated with Brittany
Brittany (; french: link=no, Bretagne ; br, Breizh, or ; Gallo language, Gallo: ''Bertaèyn'' ) is a peninsula and cultural region in the west of France, covering the western part ...

''un'' (one).
As a number

One, sometimes referred to as unity, is the first non-zeronatural number
In mathematics, the natural numbers are those numbers used for counting (as in "there are ''six'' coins on the table") and total order, ordering (as in "this is the ''third'' largest city in the country"). In common mathematical terminology, w ...

. It is thus the integer
An integer (from the Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Re ...

after zero
0 (zero) is a number
A number is a mathematical object used to counting, count, measurement, measure, and nominal number, label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in languag ...

.
Any number multiplied by one remains that number, as one is the identity
Identity may refer to:
Social sciences
* Identity (social science), personhood or group affiliation in psychology and sociology
Group expression and affiliation
* Cultural identity, a person's self-affiliation (or categorization by others ...

for multiplication
Multiplication (often denoted by the cross symbol , by the mid-line dot operator , by juxtaposition
Juxtaposition is an act or instance of placing two elements close together or side by side. This is often done in order to compare/contr ...

. As a result, 1 is its own factorial
In mathematics, the factorial of a non-negative denoted is the Product (mathematics), product of all positive integers less than or equal The factorial also equals the product of n with the next smaller factorial:
\begin
n! &= n \times (n ...

, its own square
In Euclidean geometry, a square is a regular
The term regular can mean normal or in accordance with rules. It may refer to:
People
* Moses Regular (born 1971), America football player
Arts, entertainment, and media Music
* Regular (Badfinger ...

and square root
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis) ...

, its own cube
In geometry
Geometry (from the grc, γεωμετρία; ' "earth", ' "measurement") is, with , one of the oldest branches of . It is concerned with properties of space that are related with distance, shape, size, and relative position ...

and cube root
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). ...

, and so on. One is also the result of the empty product
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It ...

, as any number multiplied by one is itself. It is also the only natural number that is neither composite
Composite or compositing may refer to:
Materials
* Composite material, a material that is made from several different substances
** Metal matrix composite, composed of metal and other parts
** Cermet, a composite of ceramic and metallic materials
* ...

nor prime
A prime number (or a prime) is a natural number greater than 1 that is not a Product (mathematics), 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 ...

with respect to 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 o ...

, but is instead considered a unit
Unit may refer to:
Arts and entertainment
* UNIT
Unit may refer to:
Arts and entertainment
* UNIT, a fictional military organization in the science fiction television series ''Doctor Who''
* Unit of action, a discrete piece of action (or beat) in ...

(meaning of ring theory
In algebra, ring theory is the study of ring (mathematics), rings—algebraic structures in which addition and multiplication are defined and have similar properties to those operations defined for the integers. Ring theory studies the structure ...

).
As a digit

The glyph used today in the Western world to represent the number 1, a vertical line, often with aserif
In typography
Typography is the art and technique of arranging type to make written language
A written language is the representation of a spoken or gestural language
A language is a structured system of communication used by ...

at the top and sometimes a short horizontal line at the bottom, traces its roots back to the Brahmic
The Brahmic scripts, also known as Indic scripts, are a family of abugida writing systems. They are used throughout the Indian subcontinent, Southeast Asia and parts of East Asia, including Japan in the form of Siddhaṃ script, Siddhaṃ. T ...

script of ancient India, where it was a simple vertical line. It was transmitted to Europe via Arabic
Arabic (, ' or , ' or ) is a Semitic language
The Semitic languages are a branch of the Afroasiatic language family originating in the Middle East
The Middle East is a list of transcontinental countries, transcontinental region ...

during the Middle Ages.
In some countries, the serif at the top is sometimes extended into a long upstroke, sometimes as long as the vertical line, which can lead to confusion with the glyph for seven
7 is a number, numeral, and glyph.
7 or seven may also refer to:
* AD 7, the seventh year of the AD era
* 7 BC, the seventh year before the AD era
* The month of July
Music Artists
* Seven (Swiss singer) (born 1978), a Swiss recording artist
* Se ...

in other countries. Whereas the digit 1 is written with a long upstroke, the digit 7 has a horizontal stroke through the vertical line.
While the shape of the character for the digit 1 has an ascenderAscender may refer to:
*Ascender (climbing), a rope-climbing device
*Ascender Corporation, a font company
*Ascender (typography), a font feature
*XP-55 Ascender, a prototype aircraft
*Isuzu Ascender, a sports utility vehicle
*JP Aerospace#Ascender, ...

in most modern typeface
A typeface is the design of lettering
Lettering is an umbrella term
In linguistics
Linguistics is the science, scientific study of language. It encompasses the analysis of every aspect of language, as well as the methods for studying ...

s, in typefaces with text figures
, a typeface designed in 1991, uses text figures.
.
Text figures (also known as non-lining, lowercase, old style, ranging, hanging, medieval, billing, or antique figures or numerals) are numeral system, numerals designed with varying heights in a ...

, the glyph usually is of x-height
upright 2.0, alt=A diagram showing the line terms used in typography
In typography
File:metal movable type.jpg, 225px, Movable type being assembled on a composing stick using pieces that are stored in the type case shown below it
Typography ...

, as, for example, in .
Many older typewriters do not have a separate symbol for ''1'', and use the lowercase letter ''l'' instead. It is possible to find cases when the uppercase ''J'' is used, while it may be for decorative purposes.
Mathematics

Definitions

Mathematically, 1 is: *inarithmetic
Arithmetic (from the Ancient Greek, Greek wikt:en:ἀριθμός#Ancient Greek, ἀριθμός ''arithmos'', 'number' and wikt:en:τική#Ancient Greek, τική wikt:en:τέχνη#Ancient Greek, έχνη ''tiké échne', 'art' or 'cra ...

(algebra
Algebra (from ar, الجبر, lit=reunion of broken parts, bonesetting, translit=al-jabr) is one of the areas of mathematics, broad areas of mathematics, together with number theory, geometry and mathematical analysis, analysis. In its most ge ...

) and calculus
Calculus, originally called infinitesimal calculus or "the calculus of infinitesimals", is the mathematics, mathematical study of continuous change, in the same way that geometry is the study of shape and algebra is the study of generalizations ...

, the natural number
In mathematics, the natural numbers are those numbers used for counting (as in "there are ''six'' coins on the table") and total order, ordering (as in "this is the ''third'' largest city in the country"). In common mathematical terminology, w ...

that follows and the multiplicative identity element
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It h ...

of the integer
An integer (from the Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Re ...

s, real number
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). ...

s and complex number
In mathematics, a complex number is an element of a number system that contains the real numbers and a specific element denoted , called the imaginary unit, and satisfying the equation . Moreover, every complex number can be expressed in the for ...

s;
*more generally, in algebra
Algebra (from ar, الجبر, lit=reunion of broken parts, bonesetting, translit=al-jabr) is one of the areas of mathematics, broad areas of mathematics, together with number theory, geometry and mathematical analysis, analysis. In its most ge ...

, the multiplicative identity (also called ''unity''), usually of a group
A group is a number
A number is a mathematical object used to counting, count, measurement, measure, and nominal number, label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with ...

or a ring.
Formalizations of the natural numbers have their own representations of 1. In the Peano axioms
In mathematical logic
Mathematical logic is the study of formal logic within mathematics. Major subareas include model theory, proof theory, set theory, and recursion theory. Research in mathematical logic commonly addresses the mathematical pr ...

, 1 is the successor
Successor is someone who, or something which succeeds or comes after (see success (disambiguation), success and Succession (disambiguation), succession)
Film and TV
* The Successor (film), ''The Successor'' (film), a 1996 film including Laura Girli ...

of 0. In ''Principia Mathematica
Image:Principia Mathematica 54-43.png, 500px, ✸54.43:
"From this proposition it will follow, when arithmetical addition has been defined, that 1 + 1 = 2." – Volume I, 1st editionp. 379(p. 362 in 2nd edition; p. 360 in abridged v ...

'', it is defined as the set of all singletons (sets with one element), and in the Von Neumann cardinal assignment
The von Neumann cardinal assignment is a cardinal assignment which uses ordinal number
In set theory, an ordinal number, or ordinal, is one generalization of the concept of a natural number that is used to describe a way to arrange a (possibly ...

of natural numbers, it is defined as the set .
In a multiplicative group
A group is a number
A number is a mathematical object used to counting, count, measurement, measure, and nominal number, label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with ...

or monoid
In abstract algebra
In algebra, which is a broad division of mathematics, abstract algebra (occasionally called modern algebra) is the study of algebraic structures. Algebraic structures include group (mathematics), groups, ring (mathematic ...

, the identity element
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It h ...

is sometimes denoted 1, but ''e'' (from the German ''Einheit'', "unity") is also traditional. However, 1 is especially common for the multiplicative identity of a ring, i.e., when an addition and 0 are also present. When such a ring has characteristic
Characteristic (from the Greek word for a property, attribute or trait
Trait may refer to:
* Phenotypic trait in biology, which involve genes and characteristics of organisms
* Trait (computer programming), a model for structuring object-oriented ...

''n'' not equal to 0, the element called 1 has the property that (where this 0 is the additive identity of the ring). Important examples are finite field
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It ...

s.
By definition, 1 is the magnitude
Magnitude may refer to:
Mathematics
*Euclidean vector, a quantity defined by both its magnitude and its direction
*Magnitude (mathematics), the relative size of an object
*Norm (mathematics), a term for the size or length of a vector
*Order of ...

, absolute value
In , the absolute value or modulus of a , denoted , is the value of without regard to its . Namely, if is , and if is (in which case is positive), and . For example, the absolute value of 3 is 3, and the absolute value of − ...

, or norm
Norm, the Norm or NORM may refer to:
In academic disciplines
* Norm (geology), an estimate of the idealised mineral content of a rock
* Norm (philosophy)
Norms are concepts ( sentences) of practical import, oriented to effecting an action, rat ...

of a unit complex number
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). I ...

, unit vector
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It ...

, and a unit matrix
In linear algebra, the identity matrix of size ''n'' is the ''n'' × ''n'' square matrix
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structur ...

(more usually called an identity matrix). Note that the term ''unit matrix'' is sometimes used to mean something quite different.
By definition, 1 is the probability
Probability is the branch of mathematics
Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained ...

of an event that is absolutely or almost certain
In probability theory
Probability theory is the branch of mathematics concerned with probability. Although there are several different probability interpretations, probability theory treats the concept in a rigorous mathematical manner by expre ...

to occur.
In category theory
Category theory formalizes mathematical structure
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and ...

, 1 is sometimes used to denote the terminal object
In category theory
Category theory formalizes mathematical structure and its concepts in terms of a Graph labeling, labeled directed graph called a ''Category (mathematics), category'', whose nodes are called ''objects'', and whose labelled d ...

of a category
Category, plural categories, may refer to:
Philosophy and general uses
*Categorization
Categorization is the ability and activity to recognize shared features or similarities between the elements of the experience of the world (such as O ...

.
In number theory
Number theory (or arithmetic or higher arithmetic in older usage) is a branch of devoted primarily to the study of the s and . German mathematician (1777–1855) said, "Mathematics is the queen of the sciences—and number theory is the queen ...

, 1 is the value of Legendre's constant
File:Legendre's constant 10 000 000.svg, 250px, Later elements up to 10,000,000 of the same sequence ''an'' = ln(''n'') − ''n''/''π''(''n'') (red line) appear to be consistently less than 1.08366 (blue line).
Legendre's cons ...

, which was introduced in 1808 by Adrien-Marie Legendre
Adrien-Marie Legendre (; ; 18 September 1752 – 9 January 1833) was a French mathematician who made numerous contributions to mathematics. Well-known and important concepts such as the Legendre polynomials and Legendre transformation are named a ...

in expressing the asymptotic behavior
In mathematical analysis, asymptotic analysis, also known as asymptotics, is a method of describing Limit (mathematics), limiting behavior.
As an illustration, suppose that we are interested in the properties of a function as becomes very large ...

of the prime-counting function
In mathematics, the prime-counting function is the Function (mathematics), function counting the number of prime numbers less than or equal to some real number ''x''. It is denoted by (''x'') (unrelated to the pi, number ).
Image:PrimePi.svg, 400p ...

. Legendre's constant was originally conjectured to be approximately 1.08366, but was proven to equal exactly 1 in 1899.
Properties

Tallying is often referred to as "base 1", since only one mark – the tally itself – is needed. This is more formally referred to as aunary numeral system
The unary numeral system is the simplest numeral system to represent natural numbers: to represent a number ''N'', a symbol representing 1 is repeated ''N'' times.
In the unary system, the number 0 (zero) is represented by the empty string, that ...

. Unlike base 2
Base or BASE may refer to:
Brands and enterprises
*Base (mobile telephony provider), a Belgian mobile telecommunications operator
*Base CRM, an enterprise software company founded in 2009 with offices in Mountain View and Kraków, Poland
*Base De ...

or base 10
The decimal numeral system (also called the base-ten positional numeral system, and occasionally called denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hi ...

, this is not a positional notation
Positional notation (or place-value notation, or positional numeral system) usually denotes the extension to any of the (or ). More generally, a positional system is a numeral system in which the contribution of a digit to the value of a number ...

.
Since the base 1 exponential function (1inverse
Inverse or invert may refer to:
Science and mathematics
* Inverse (logic), a type of conditional sentence which is an immediate inference made from another conditional sentence
* Additive inverse (negation), the inverse of a number that, when add ...

does not exist (which would be called the logarithm
In mathematics
Mathematics (from Greek: ) includes the study of such topics as numbers ( and ), formulas and related structures (), shapes and spaces in which they are contained (), and quantities and their changes ( and ). There is no ...

base 1 if it did exist).
There are two ways to write the real number 1 as a recurring decimal
A repeating decimal or recurring decimal is decimal representation
A decimal representation of a non-negative real number
Real may refer to:
* Reality, the state of things as they exist, rather than as they may appear or may be thought to be
C ...

: as 1.000..., and as 0.999.... 1 is the first figurate numberThe 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
* polygon ...

of every kind, such as triangular number
A triangular number or triangle number counts objects arranged in an equilateral triangle. Triangular numbers are a type of figurate number, other examples being square numbers and Cube (algebra)#In integers, cube numbers. The th triangular number ...

, pentagonal number 181px, A visual representation of the first six pentagonal numbers
A pentagonal number is a figurate number that extends the concept of triangular number, triangular and square numbers to the pentagon, but, unlike the first two, the patterns involv ...

and centered hexagonal number
A centered hexagonal number, or hex number, is a centered figurate number that represents a hexagon
In geometry
Geometry (from the grc, γεωμετρία; ''wikt:γῆ, geo-'' "earth", ''wikt:μέτρον, -metron'' "measurement") ...

, to name just a few.
In many mathematical and engineering problems, numeric values are typically ''normalized'' to fall within the unit interval
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). I ...

from 0 to 1, where 1 usually represents the maximum possible value in the range of parameters. Likewise, vectors
Vector may refer to:
Biology
*Vector (epidemiology), an agent that carries and transmits an infectious pathogen into another living organism; a disease vector
*Vector (molecular biology), a DNA molecule used as a vehicle to artificially carr ...

are often normalized into unit vector
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It ...

s (i.e., vectors of magnitude one), because these often have more desirable properties. Functions, too, are often normalized by the condition that they have integral
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). ...

one, maximum value one, or square integral one, depending on the application.
Because of the multiplicative identity, if ''f''(''x'') is a multiplicative function
:''Outside number theory, the term multiplicative function is usually used for completely multiplicative functions. This article discusses number theoretic multiplicative functions.''
In number theory, a multiplicative function is an arithmetic ...

, then ''f''(1) must be equal to 1.
It is also the first and second number in the Fibonacci
Fibonacci (; also , ; – ), also known as Leonardo Bonacci, Leonardo of Pisa, or Leonardo Bigollo Pisano ('Leonardo the Traveller from Pisa'), was an Italian mathematician
A mathematician is someone who uses an extensive knowledge of mathem ...

sequence (0 being the zeroth) and is the first number in many other .
The definition of a field
Field may refer to:
Expanses of open ground
* Field (agriculture), an area of land used for agricultural purposes
* Airfield, an aerodrome that lacks the infrastructure of an airport
* Battlefield
* Lawn, an area of mowed grass
* Meadow, a grassl ...

requires that 1 must not be equal to . Thus, there are no fields of characteristic 1. Nevertheless, abstract algebra can consider the field with one element
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It h ...

, which is not a singleton and is not a set at all.
1 is the most common leading digit in many sets of data, a consequence of Benford's law.
1 is the only known Tamagawa numberIn mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It ha ...

for a simply connected algebraic group over a number field.
The generating function
In mathematics, a generating function is a way of encoding an infinite sequence of numbers (''a'n'') by treating them as the coefficients of a formal power series. This series is called the generating function of the sequence. Unlike an ordinar ...

that has all coefficients 1 is given by
$\backslash frac\; =\; 1+x+x^2+x^3+\; \backslash ldots$
This power series converges and has finite value if and only if
In logic
Logic is an interdisciplinary field which studies truth and reasoning
Reason is the capacity of consciously making sense of things, applying logic
Logic (from Ancient Greek, Greek: grc, wikt:λογική, λογική, l ...

$,\; x,\; <\; 1$.
Primality

1 is by convention neither aprime number
A prime number (or a prime) is a natural number greater than 1 that is not a Product (mathematics), 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 ...

nor a composite number
A composite number is a positive integer
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculu ...

, but a unit
Unit may refer to:
Arts and entertainment
* UNIT
Unit may refer to:
Arts and entertainment
* UNIT, a fictional military organization in the science fiction television series ''Doctor Who''
* Unit of action, a discrete piece of action (or beat) in ...

(meaning of ring theory
In algebra, ring theory is the study of ring (mathematics), rings—algebraic structures in which addition and multiplication are defined and have similar properties to those operations defined for the integers. Ring theory studies the structure ...

) like −1 and, in the Gaussian integers
In number theory, a Gaussian integer is a complex number
In mathematics, a complex number is a number that can be expressed in the form , where and are real numbers, and is a symbol (mathematics), symbol called the imaginary unit, and satisf ...

, '' i'' and −''i''.
The fundamental theorem of arithmetic
In number theory, the fundamental theorem of arithmetic, also called the unique factorization theorem or the unique-prime-factorization theorem, states that every integer
An integer (from the Latin wikt:integer#Latin, ''integer'' meaning "wh ...

guarantees unique factorization
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It ...

over the integers only up to units. For example, , but if units are included, is also equal to, say, among infinitely many similar "factorizations".
1 appears to meet the naïve definition of a prime number, being evenly divisible only by 1 and itself (also 1). As such, some mathematicians considered it a prime number as late as the middle of the 20th century, but mathematical consensus has generally and since then universally been to exclude it for a variety of reasons (such as complicating the fundamental theorem of arithmetic and other theorems related to prime numbers).
1 is the only positive integer divisible by exactly one positive integer, whereas prime numbers are divisible by exactly two positive integers, composite numbers are divisible by more than two positive integers, and zero
0 (zero) is a number
A number is a mathematical object used to counting, count, measurement, measure, and nominal number, label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in languag ...

is divisible by all positive integers.
Table of basic calculations

In technology

* Theresin identification code
The ASTM International Resin Identification Coding System, often abbreviated RIC, is a set of symbols appearing on plastic
Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ing ...

used in recycling to identify polyethylene terephthalate
Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic
A thermoplastic, or thermosoft plastic, is a plastic polymer
A polymer (; Greek ''wikt:poly-, poly-' ...

.
*The ITU
260px, ITU Monument, Bern
The International Telecommunication Union is a specialized agency of the United Nations responsible for all matters related to information and communication technologies
Information and communications technology ...

country code for the North American Numbering Plan
The North American Numbering Plan (NANP) is a telephone numbering plan
A telephone numbering plan is a type of numbering schemeThere are many different numbering schemes for assigning nominal numbers to entities. These generally require an agr ...

area, which includes the United States, Canada, and parts of the Caribbean.
*A binary code
A binary code represents text
Text may refer to:
Written word
* Text (literary theory)
Text may refer to:
Written word
* Text (literary theory), any object that can be read, including:
**Religious text, a writing that a religious tradition con ...

is a sequence of 1 and that is used in computer
A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic sets of operations known as Computer program, programs. These ...

s for representing any kind of data
Data (; ) are individual facts, statistics, or items of information, often numeric. In a more technical sense, data are a set of values of qualitative property, qualitative or quantity, quantitative variable (research), variables about one or ...

.
*In many physical devices, 1 represents the value for "on", which means that electricity is flowing.
*The numerical value of true
True most commonly refers to truth
Truth is the property of being in accord with fact or reality.Merriam-Webster's Online Dictionarytruth 2005 In everyday language, truth is typically ascribed to things that aim to represent reality or otherw ...

in many programming languages.
*1 is the ASCII
ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding
In computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the stu ...

code of " Start of Header".
In science

*Dimensionless quantities
In dimensional analysis
In engineering
Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline ...

are also known as quantities of dimension one.
*1 is the atomic number of hydrogen
Hydrogen is the chemical element
Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements
In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

.
*+1 is the electric charge
Electric charge is the physical property
A physical property is any property
Property is a system of rights that gives people legal control of valuable things, and also refers to the valuable things themselves. Depending on the nature of th ...

of positron
The positron or antielectron is the antiparticle
s (left) and antiparticles (right). From top to bottom; electron
The electron is a subatomic particle, symbol or , whose electric charge
Electric charge is the physical property of mat ...

s and protons.
*Group 1 of the periodic table
The periodic table, also known as the periodic table of (the) chemical elements, is a tabular display of the chemical element
upright=1.0, 500px, The chemical elements ordered by link=Periodic table
In chemistry
Chemistry is ...

consists of the alkali metals
The alkali metals consist of the chemical element
upright=1.0, 500px, The chemical elements ordered by link=Periodic table
In chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a ...

.
*Period 1 of the periodic table consists of just two elements, hydrogen
Hydrogen is the chemical element
Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements
In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

and helium
Helium (from el, ἥλιος, helios
Helios; Homeric Greek: ), Latinized as Helius; Hyperion and Phaethon are also the names of his father and son respectively. often given the epithets Hyperion ("the one above") and Phaethon ("the shining") ...

.
*The dwarf planet Ceres
Ceres most commonly refers to:
* Ceres (dwarf planet)
Ceres (; minor-planet designation: 1 Ceres) is the smallest recognized dwarf planet, the closest dwarf planet to the Sun, and the List of notable asteroids, largest object in the main astero ...

has the minor-planet designation 1 Ceres because it was the first asteroid to be discovered.
*The Roman numeral I often stands for the first-discovered satellite of a planet
A planet is an astronomical body orbiting a star or Stellar evolution#Stellar remnants, stellar remnant that is massive enough to be Hydrostatic equilibrium, rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and ...

or minor planet
A minor planet is an astronomical object in direct orbit around the Sun (or more broadly, any star with a planetary system) that is neither a planet nor exclusively classified as a comet. Before 2006, the International Astronomical Union (IAU) o ...

(such as Neptune I, a.k.a. Triton
Triton commonly refers to:
* Triton (mythology), a Greek god
* Triton (moon), a satellite of Neptune
Triton may also refer to:
Biology
* Triton cockatoo, a parrot
* Triton (gastropod), a group of sea snails
* ''Triton'', a synonym of ''Triturus'', ...

). For some earlier discoveries, the Roman numerals originally reflected the increasing distance from the primary instead.
In philosophy

In the philosophy ofPlotinus
Plotinus (; grc-gre, Πλωτῖνος, ''Plōtînos''; – 270 CE) was a major Hellenistic
The Hellenistic period spans the period of Mediterranean history
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surround ...

(and that of other neoplatonist
Neoplatonism is a strand of Platonic
Plato's influence on Western culture was so profound that several different concepts are linked by being called Platonic or Platonist, for accepting some assumptions of Platonism, but which do not imply accept ...

s), is the ultimate reality and source of all existence. Philo of Alexandria
Philo of Alexandria (; grc, Φίλων, Phílōn; he, , Yedidia (Jedediah) HaCohen; ), also called Philo Judaeus, was a Hellenistic Jewish philosopher
A philosopher is someone who practices philosophy. The term ''philosopher'' comes from ...

(20 BC – AD 50) regarded the number one as God's number, and the basis for all numbers ("De Allegoriis Legum," ii.12 .66.
In literature

*Number One is a character in the book series ''Lorien Legacies
''Lorien Legacies'' is a series of young adult fiction, 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''
"I ...

'' by Pittacus Lore.
*Number 1 is also a character in the series ''Artemis Fowl
''The Fowl Adventures'' is a series of ten dark fantasy novels written by Irish people, Irish author Eoin Colfer revolving around various members of the Fowl family. The first cycle, ''Artemis Fowl'', follows Elf (Artemis Fowl), elf LEP Reconn ...

'' by Eoin Colfer
Eoin Colfer (; born 14 May 1965) is an Irish author of children's books. He worked as a primary school teacher before he became a full-time writer. He is best known for being the author of the ''Artemis Fowl'' series. In September 2008, Colf ...

.
In music

*In a 1968 song byHarry Nilsson
Harry Edward Nilsson III (June 15, 1941 – January 15, 1994), known professionally as Nilsson, was an American singer-songwriter who achieved the peak of his commercial success in the early 1970s. His work is characterized by pioneering vocal o ...

and recorded by Three Dog Night
Three Dog Night is an American rock band formed in 1967, with founding members consisting of vocalists Danny Hutton, Cory Wells, and Chuck Negron. This lineup was soon augmented by Jimmy Greenspoon (keyboards), Joe Schermie (bass), Michael Al ...

, the number one is identified as "the loneliest number".
*''We Are Number One
"We Are Number One" is a song from the English-language Iceland
Iceland ( is, Ísland; ) is a Nordic countries, Nordic island country in the Atlantic Ocean, North Atlantic Ocean, with a population of 356,991 and an area of , making it the m ...

'' is a 2014 song from the children's TV show ''LazyTown
''LazyTown'' (Icelandic: ''Latibær'') is an Icelandic-American children's television musical series. It was created by Magnús Scheving
Magnús Örn Eyjólfsson Scheving (; born 10 November 1964) is an Icelandic writer, entrepreneur, produce ...

'', which gained popularity as a meme
A meme ( ) is an idea, behavior, or style that spreads by means of imitation from person to person within a culture and often carries symbolic meaning representing a particular phenomenon or theme. A meme acts as a unit for carrying culture, c ...

.
* ''1'' (Beatles album), a compilation album by the Beatles.
* One
1 (one, also called unit, and unity) is a number
A number is a mathematical object used to counting, count, measurement, measure, and nominal number, label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can ...

, a 1991 song by Irish rock band .
In comics

*A character in the Italian comic book Alan Ford (authorsMax Bunker
Max Bunker, pen name of Luciano Massimiliano Secchi (born 24 August 1939), is an Italian comics, Italian comic book writer, and publisher, best known as the co-author of ''Alan Ford (comics), Alan Ford''.
Bunker's career started in 1960 when he co- ...

and Magnus
Magnus, meaning "Great" in Latin, was used as of in the first century BCE. The best-known use of the name during the Roman Empire is for the fourth-century Western Roman Emperor Flavius Magnus the assassin, often just called . The name gained ...

), very old disabled man, the supreme leader of the group TNT.
*A character in the Italian comic series PKNA
''PK - Paperinik New Adventures'' (''PKNA'') is an Italian comic, published by Disney Italy from 14 March 1996 to 20 December 2000, about the new adventures of Paperinik, the superhero
A superhero or superheroine is a stock character that p ...

and its sequels, an artificial intelligence
Artificial intelligence (AI) is intelligence
Intelligence has been defined in many ways: the capacity for abstraction
Abstraction in its main sense is a conceptual process where general rules and concept
Concepts are defined as abstra ...

as an ally of the protagonist PaperinikDonald Duck
Donald Fauntleroy Duck is a cartoon character created in 1934 at Walt Disney Animation Studios. Donald is an Anthropomorphism, anthropomorphic American Pekin, white duck with a yellow-orange bill, legs, and feet. He typically wears a ...

.
In sports

*Inbaseball
Baseball is a bat-and-ball games, bat-and-ball game played between two opposing teams who take turns batting (baseball), batting and fielding. The game proceeds when a player on the fielding team (baseball), fielding team, called the pi ...

scoring, the number 1 is assigned to the pitcher
In baseball, the pitcher is the player who pitches the Baseball (ball), baseball from the pitcher's mound toward the catcher to begin each play, with the goal of out (baseball), retiring a batter (baseball), batter, who attempts to either make ...

.
*In association football
Association football, more commonly known as simply football or soccer, is a team sport played with a sphere, spherical Ball (association football), ball between two teams of 11 football player, players. It is played by approximately 250&nbs ...

(soccer) the number 1 is often given to the goalkeeper
In many team sports which involve scoring goal (sport), goals, the goalkeeper (sometimes termed goaltender, netminder, goalie or keeper) is a designated player charged with directly preventing the opposing team from scoring by blocking or inte ...

.
*In most competitions of rugby league
Rugby league football, commonly known as just rugby league or simply league, rugby, football, or footy, is a full-contact sport played by two teams of thirteen players on a rectangular field
Field may refer to:
Expanses of open ground
* Fi ...

(though not the Super League
The Super League (SL), sponsored as the Betfred Super League and officially known as Super League Europe, is the top-level of the British rugby league system. At present the league consists of twelve teams, of which ten are from Northern Engl ...

, which uses static squad numbering), the starting fullback wears jersey number 1.
*In rugby union
Rugby union, commonly known simply as rugby, is a Contact sport#Terminology, close-contact team sport that originated in England in the first half of the 19th century. One of the Comparison of rugby league and rugby union, two codes of rugby f ...

, the starting wears the jersey number 1.
*1 is the lowest number permitted for use by players of the National Hockey League
The National Hockey League (NHL; french: Ligue nationale de hockey—LNH) is a professional ice hockey sports league, league in North America comprising 32 teams—25 in the United States and 7 in Canada. It is considered to be the premier pro ...

(NHL); the league prohibited the use of 00 and 0 in the late 1990s (the highest number permitted being 98).
*1 is the lowest number
A number is a mathematical object
A mathematical object is an abstract concept arising in mathematics.
In the usual language of mathematics, an ''object'' is anything that has been (or could be) formally defined, and with which one may do deduct ...

permitted for use at most levels of American football
American football, referred to simply as football in the United States and Canada and also known as gridiron, is a team sport
A team sport includes any sport
Sport pertains to any form of Competition, competitive physical acti ...

. Under National Football League
The National Football League (NFL) is a professional American football
American football, referred to simply as football in the United States and also known as gridiron, is a team sport played by two teams of eleven players on a rect ...

policy, it can only be used by a quarterback
The quarterback (commonly abbreviated "QB"), colloquially known as the "signal caller", is a position in gridiron football
Gridiron football,

or kicking player (during preseason play, restrictions are looser, and players of other positions can wear the number and can also, if no other options exist, wear 0).
*In Formula One
Formula One (also known as Formula 1 or F1) is the highest class of international racing for Open wheel car, single-seater Formula racing, formula racing cars sanctioned by the Fédération Internationale de l'Automobile (FIA). The World Dri ...

, the previous year's world champion is allowed to use the number 1.
In film

*'' One A.M.'' (1916), starringCharlie Chaplin
Sir Charles Spencer Chaplin Jr. (16 April 188925 December 1977) was an English comic actor, filmmaker, and composer who rose to fame in the era of . He became a worldwide icon through his screen persona, , and is considered one of the most i ...

.
*'' One More Time'' (1970), directed by Jerry Lewis
Jerry Lewis (born Joseph Levitch; March 16, 1926 – August 20, 2017) was an American comedian, actor, filmmaker, humanitarian and singer. Nicknamed "The King of Comedy", he is regarded as one of the most significant American cultural figur ...

and starring Sammy Davis Jr.
Samuel George Davis Jr. (December 8, 1925 – May 16, 1990) was an American singer, dancer, actor, vaudevillian and comedian whom critic Randy Blaser called "the greatest entertainer ever to grace a stage in these United States".
At age th ...

and Peter Lawford
Peter Sydney Ernest Lawford (born Peter Sydney Ernest Aylen; 7 September 1923 – 24 December 1984) was an English-born American actor, producer, and socialite, who resided in the United States throughout his adult life.Obituary ''Variety Obitua ...

.
*'' One Day'' (2011), starring Anne Hathaway
Anne Jacqueline Hathaway (born November 12, 1982) is an American actress. She is the recipient of many awards, including an Academy Award
The Academy Awards, popularly known as the Oscars, are awards for artistic and technical merit in ...

and Jim Sturgess
James Anthony Sturgess''Births, Marriages & Deaths Index of England & Wales, 1916–2005.''; at ancestry.com (born 16 May 1978) is an English actor and singer-songwriter. His first major role was as Jude in the musical romance drama film '' Acr ...

.
In other fields

*''Number One'' isRoyal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare
Naval warfare is combat
Combat ( French for ''fight'') is a purposeful violent conflict meant to physically harm or kill the opposition. Combat may be armed (using weapon
A ...

informal usage for the chief executive officer of a ship, the captain's deputy responsible for discipline and all normal operation of a ship and its crew.
*1 is the value of an ace
An ace is a playing card
A playing card is a piece of specially prepared , heavy paper, thin cardboard, , cotton-paper blend, or thin plastic that is marked with distinguishing motifs. Often the front (face) and back of each card has a to ...

in many playing card games, such as cribbage
Cribbage, or crib, is a card game, traditionally for two players, that involves playing and grouping playing cards, cards in combinations which gain points. It can be adapted for three or four players.
Cribbage has several distinctive features ...

.
*List of highways numbered 1
The following highways are numbered 1.
For roads numbered A1, see list of A1 roads.
For roads numbered B1, see list of B1 roads.
For roads numbered M1, see List of M1 roads.
For roads numbered N1, see list of N1 roads.
For roads numbered S1 ...

* List of public transport routes numbered 1
*1 is often used to denote the Gregorian calendar
The Gregorian calendar is the used in most of the world. It was introduced in October 1582 by as a modification of the , reducing the average year from 365.25 days to 365.2425 days, and adjusting for the drift in the that the inaccuracy ha ...

month of January
January is the first month of the year in the Julian and Gregorian calendar
The Gregorian calendar is the used in most of the world. It was introduced in October 1582 by as a modification of the , reducing the average year from 365. ...

.
*1 CE
__NOTOC__
AD 1 (I), 1 AD or 1 CE is the epoch year for the Anno Domini
The terms (AD) and before Christ (BC) are used to label or number years in the Julian and Gregorian calendar
The Gregorian calendar is the calendar used in ...

, the first year of the Common Era
Common Era (CE) is one of the year notations used for the Gregorian calendar
The Gregorian calendar is the used in most of the world. It was introduced in October 1582 by as a modification of the , reducing the average year from 365.2 ...

*01, the former dialing code for Greater London
Greater London is an administrative area
Administrative division, administrative unitArticle 3(1). , country subdivision, administrative region, subnational entity, first-level subdivision, as well as many similar terms, are generic names ...

* PRS One, a German paraglider design
*+1 is the code for international telephone calls to countries in the North American Numbering Plan
The North American Numbering Plan (NANP) is a telephone numbering plan
A telephone numbering plan is a type of numbering schemeThere are many different numbering schemes for assigning nominal numbers to entities. These generally require an agr ...

.
See also

*−1
In mathematics
Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It ...

* +1 (disambiguation)
*List of mathematical constantsA mathematical constant
A mathematical constant is a key number
A number is a mathematical object used to counting, count, measurement, measure, and nominal number, label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. ...

* One (word)
*Root of unity
The 5th roots of unity (blue points) in the complex plane
In mathematics
Mathematics (from Greek: ) includes the study of such topics as numbers ( and ), formulas and related structures (), shapes and spaces in which they are containe ...

*List of highways numbered 1
The following highways are numbered 1.
For roads numbered A1, see list of A1 roads.
For roads numbered B1, see list of B1 roads.
For roads numbered M1, see List of M1 roads.
For roads numbered N1, see list of N1 roads.
For roads numbered S1 ...

References

External links

The Number 1

The Positive Integer 1

{{DEFAULTSORT:1 (Number) Integers