2 (two) is a

number A number is a mathematical object used to count, measure, and label. The most basic examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with number words. More universally, individual numbers can ...

, numeral and digit. It is the

natural number In mathematics, the natural numbers are the numbers 0, 1, 2, 3, and so on, possibly excluding 0. Some start counting with 0, defining the natural numbers as the non-negative integers , while others start with 1, defining them as the positive in ...

following 1 and preceding 3. It is the smallest and the only even

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 ...

. Because it forms the basis of a duality, it has

religious Religion is a range of social- cultural systems, including designated behaviors and practices, morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, or organizations, that generally relate humanity to supernatural ...

and spiritual significance in many

cultures Culture ( ) is a concept that encompasses the social behavior, institutions, and Social norm, norms found in human societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, Attitude (psychology), attitudes ...

Mathematics

The number 2 is the second natural number after 1. Each natural number, including 2, is constructed by succession, that is, by adding 1 to the previous natural number. 2 is the smallest and the only even

, and the first

Ramanujan prime In mathematics, a Ramanujan prime is a prime number that satisfies a result proven by Srinivasa Ramanujan relating to the prime-counting function. Origins and definition In 1919, Ramanujan published a new proof of Bertrand's postulate which, as ...

. It is also the first

superior highly composite number In number theory, a superior highly composite number is a natural number which, in a particular rigorous sense, has many divisors. Particularly, it is defined by a ratio between the number of divisors an integer has and that integer raised to s ...

, and the first

colossally abundant number In number theory, a colossally abundant number (sometimes abbreviated as CA) is a natural number that, in a particular, rigorous sense, has many divisors. Particularly, it is defined by a ratio between the sum of an integer's divisors and that ...

. An

integer An integer is the number zero (0), a positive natural number (1, 2, 3, ...), or the negation of a positive natural number (−1, −2, −3, ...). The negations or additive inverses of the positive natural numbers are referred to as negative in ...

is determined to be

even Even may refer to: General * Even (given name), a Norwegian male personal name * Even (surname), a Breton surname * Even (people), an ethnic group from Siberia and Russian Far East **Even language, a language spoken by the Evens * Odd and Even, a ...

if it is

divisible 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 divisibl ...

by two. When written in base 10, all

multiples Multiple may refer to: Economics *Multiple finance, a method used to analyze stock prices *Multiples of the price-to-earnings ratio *Chain stores, are also referred to as 'Multiples' *Box office multiple, the ratio of a film's total gross to tha ...

of 2 will end in 0, 2, 4, 6, or 8; more generally, in any even base, even numbers will end with an even digit. A

digon In geometry, a bigon, digon, or a ''2''-gon, is a polygon with two sides (edge (geometry), edges) and two Vertex (geometry), vertices. Its construction is Degeneracy (mathematics), degenerate in a Euclidean plane because either the two sides wou ...

is a polygon with two sides (or

edges Enhanced Data rates for GSM Evolution (EDGE), also known as 2.75G and under various other names, is a 2G digital mobile phone technology for packet switched data transmission. It is a subset of General Packet Radio Service (GPRS) on the GS ...

) and two vertices. Two distinct

points A point is a small dot or the sharp tip of something. Point or points may refer to: Mathematics * Point (geometry), an entity that has a location in space or on a plane, but has no extent; more generally, an element of some abstract topologica ...

in a

plane Plane most often refers to: * Aero- or airplane, a powered, fixed-wing aircraft * Plane (geometry), a flat, 2-dimensional surface * Plane (mathematics), generalizations of a geometrical plane Plane or planes may also refer to: Biology * Plane ...

are always

sufficient In logic and mathematics, necessity and sufficiency are terms used to describe a conditional or implicational relationship between two statements. For example, in the conditional statement: "If then ", is necessary for , because the truth of ...

to define a unique line in a nontrivial

Euclidean space Euclidean space is the fundamental space of geometry, intended to represent physical space. Originally, in Euclid's ''Elements'', it was the three-dimensional space of Euclidean geometry, but in modern mathematics there are ''Euclidean spaces ...

. A

set Set, The Set, SET or SETS may refer to: Science, technology, and mathematics Mathematics *Set (mathematics), a collection of elements *Category of sets, the category whose objects and morphisms are sets and total functions, respectively Electro ...

that is 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 grass ...

has a minimum of two elements.

Binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two values (0 and 1) for each digit * Binary function, a function that takes two arguments * Binary operation, a mathematical op ...

is a number system with a base of two, it is used extensively in

computing Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, hardware and softw ...

As a word

''Two'' is most commonly a

determiner Determiner, also called determinative ( abbreviated ), is a term used in some models of grammatical description to describe a word or affix belonging to a class of noun modifiers. A determiner combines with a noun to express its reference. Examp ...

used with

plural In many languages, a plural (sometimes list of glossing abbreviations, abbreviated as pl., pl, , or ), is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a quantity greater than ...

countable nouns, as in ''two days'' or ''I'll take these two''. ''Two'' is a

noun In grammar, a noun is a word that represents a concrete or abstract thing, like living creatures, places, actions, qualities, states of existence, and ideas. A noun may serve as an Object (grammar), object or Subject (grammar), subject within a p ...

when it refers to the number two as in ''two plus two is four.'' The word ''two'' is derived from the

Old English Old English ( or , or ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the Early Middle Ages. It developed from the languages brought to Great Britain by Anglo-S ...

words (

feminine Femininity (also called womanliness) is a set of attributes, behaviors, and Gender roles, roles generally associated with women and girls. Femininity can be understood as Social construction of gender, socially constructed, and there is also s ...

), (neuter), and (masculine, which survives today in the form

twain TWAIN and TWAIN Direct are application programming interfaces (APIs) and communication protocols that regulate communication between software and digital imaging devices, such as image scanners and digital cameras. TWAIN is supported on Microso ...

Evolution of the Arabic digit

The digit used in the modern Western world to represent the number 2 traces its roots back to the Indic

Brahmic script The Brahmic scripts, also known as Indic scripts, are a family of abugida writing systems. They are used throughout South Asia, Southeast Asia and parts of East Asia. They are descended from the Brahmi script of ancient India and are used b ...

, where "2" was written as two horizontal lines. The modern

Chinese Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethnic ...

and

Japanese Japanese may refer to: * Something from or related to Japan, an island country in East Asia * Japanese language, spoken mainly in Japan * Japanese people, the ethnic group that identifies with Japan through ancestry or culture ** Japanese diaspor ...

languages (and Korean

Hanja Hanja (; ), alternatively spelled Hancha, are Chinese characters used to write the Korean language. After characters were introduced to Korea to write Literary Chinese, they were adapted to write Korean as early as the Gojoseon period. () ...

) still use this method. The

Gupta script The Gupta script (sometimes referred to as Gupta Brahmi script or Late Brahmi script)Sharma, Ram. '' 'Brahmi Script' ''. Delhi: BR Publishing Corp, 2002 was used for writing Sanskrit and is associated with the Gupta Empire of the Indian subcon ...

rotated the two lines 45 degrees, making them diagonal. The top line was sometimes also shortened and had its bottom end curve towards the center of the bottom line. In the Nagari script, the top line was written more like a curve connecting to the bottom line. In the Arabic Ghubar writing, the bottom line was completely vertical, and the digit looked like a dotless closing question mark. Restoring the bottom line to its original horizontal position, but keeping the top line as a curve that connects to the bottom line leads to our modern digit.

In science

* The first magic number - number of electrons in the innermost electron shell of an atom.

References

External links