2 (two) is a number, numeral and

digit Digit may refer to: Mathematics and science * Numerical digit, as used in mathematics or computer science ** Hindu-Arabic numerals, the most common modern representation of numerical digits * Digit (anatomy), the most distal part of a limb, such ...

. It is the natural number following 1 and preceding 3. It is the smallest and the only even prime number. Because it forms the basis of a

duality Duality may refer to: Mathematics * Duality (mathematics), a mathematical concept ** Dual (category theory), a formalization of mathematical duality ** Duality (optimization) ** Duality (order theory), a concept regarding binary relations ** Dual ...

, it has religious and spiritual significance in many cultures.

As a word

''Two'' is most commonly a

determiner A determiner, also called determinative (abbreviated ), is a word, phrase, or affix that occurs together with a noun or noun phrase and generally serves to express the reference of that noun or noun phrase in the context. That is, a determiner m ...

used with plural countable nouns, as in ''two days'' or ''I'll take these two''. ''Two'' is a noun when it refers to the number two as in ''two plus two is four.''

Etymology of ''two''

The word ''two'' is derived from the

Old English Old English (, ), 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 was brought to Great Britain by Anglo-Saxon settlement of Britain, Anglo ...

words (

feminine Femininity (also called womanliness) is a set of attributes, behaviors, and roles generally associated with women and girls. Femininity can be understood as socially constructed, and there is also some evidence that some behaviors considered fe ...

), (neuter), and (masculine, which survives today in the form twain). The pronunciation , like that of ''who'' is due to the

labialization Labialization is a secondary articulatory feature of sounds in some languages. Labialized sounds involve the lips while the remainder of the oral cavity produces another sound. The term is normally restricted to consonants. When vowels involve ...

of the vowel by the ''w'', which then disappeared before the related sound. The successive stages of pronunciation for the Old English would thus be , , , , and finally .

Mathematics

An integer is determined to be

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

if it is divisible by two. When written in base 10, all multiples of 2 will end in 0, 2, 4, 6, or 8. 2 is the smallest and the only even prime number, 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 ...

Geometry

A digon is a polygon with two sides (or

edges Edge or EDGE may refer to: Technology Computing * Edge computing, a network load-balancing system * Edge device, an entry point to a computer network * Adobe Edge, a graphical development application * Microsoft Edge, a web browser developed by ...

) and two vertices. Two distinct

points Point or points may refer to: Places * Point, Lewis, a peninsula in the Outer Hebrides, Scotland * Point, Texas, a city in Rains County, Texas, United States * Point, the NE tip and a ferry terminal of Lismore, Inner Hebrides, Scotland * Point ...

in a

plane Plane(s) most often refers to: * Aero- or airplane, a powered, fixed-wing aircraft * Plane (geometry), a flat, 2-dimensional surface Plane or planes may also refer to: Biology * Plane (tree) or ''Platanus'', wetland native plant * Planes (gen ...

are always sufficient to define a unique

line Line most often refers to: * Line (geometry), object with zero thickness and curvature that stretches to infinity * Telephone line, a single-user circuit on a telephone communication system Line, lines, The Line, or LINE may also refer to: Arts ...

in a nontrivial Euclidean space.

Set Theory

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 has a minimum of two

elements Element or elements may refer to: Science * Chemical element, a pure substance of one type of atom * Heating element, a device that generates heat by electrical resistance * Orbital elements, parameters required to identify a specific orbit of ...

. A Cantor space is a topological space

2^\mathbb

homeomorphic In the mathematical field of topology, a homeomorphism, topological isomorphism, or bicontinuous function is a bijective and continuous function between topological spaces that has a continuous inverse function. Homeomorphisms are the isomorphi ...

to the

Cantor set In mathematics, the Cantor set is a set of points lying on a single line segment that has a number of unintuitive properties. It was discovered in 1874 by Henry John Stephen Smith and introduced by German mathematician Georg Cantor in 1883. Thr ...

Base 2

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

List of basic calculations

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

Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of va ...

and Japanese languages (and Korean Hanja) 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 fonts with text figures, digit 2 usually is of x-height, for example, .

In science

*The number of polynucleotide strands in a DNA double helix. *The first magic number. *The atomic number of helium.

References

External links

Prime curiosities: 2
{{DEFAULTSORT:2 (Number) 2 (number) Integers