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2#In sports

{{Short description|Integer number 2}}

{{Hatnote|This article is about the number. For the years, see 2 BC and AD 2. For other uses, see II (disambiguation) and Number Two (disambiguation).}}

{{pp-vandalism|small=yes}}

{{Infobox number

|number=2

|ordinal=2nd (second)

|numeral=binary

|gaussian integer factorization = (1 + i)(1 - i)

|prime=1st

|divisor=1, 2

|roman =II, ii

|greek prefix=di-

|latin prefix=duo-/bi-

|old english prefix=twi-

|lang1=Greek numeral

|lang1 symbol=β'

|lang2=Arabic, Kurdish, Persian, Sindhi, Urdu

|lang2 symbol={{resize|150%|٢}}

|lang3=Ge'ez

|lang3 symbol=፪

|lang4=Bengali

|lang4 symbol={{resize|150%|২}}

|lang5=Chinese numeral

|lang5 symbol=二，弍，貳

|lang6=Devanāgarī

|lang6 symbol={{resize|150%|२}}

|lang7=Santali

|lang7 symbol={{resize|150%|᱒}}

|lang8=Telugu

|lang9=Tamil

|lang9 symbol={{resize|150%|௨}}

|lang10=Kannada

|lang10 symbol={{resize|150%|೨}}

|lang11=Hebrew

|lang11 symbol={{resize|150%|ב}}

|lang12=Armenian|lang12 symbol=Բ|lang13=Khmer

|lang13 symbol=២

|lang14=Maya numerals|lang14 symbol=••|lang15=Thai

|lang15 symbol=๒

|lang16=Georgian

|lang16 symbol={{resize|130%| Ⴁ/ⴁ/ბ}}(Bani)

|lang17=Malayalam

|lang17 symbol=൨

|lang18=Babylonian numeral|lang18 symbol=𒐖|lang19=Egyptian hieroglyph, Aegean numeral, Chinese counting rod|lang19 symbol={{!}}{{!}}|lang20=Morse code|lang20 symbol={{resize|150%|.._ _ _}}}}

2 (two) is a number, numeral and digit. 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, it has religious and spiritual significance in many cultures.

As a word

Two is most commonly a determiner used with plural countable nouns, as in two days or I'll take these two.{{Cite book |last1=Huddleston |first1=Rodney D. |url=https://www.worldcat.org/oclc/1255524478 |title=A student's introduction to English grammar |last2=Pullum |first2=Geoffrey K. |last3=Reynolds |first3=Brett |publisher=Cambridge University Press |year=2022 |isbn=978-1-316-51464-1 |edition=2nd |location=Cambridge, United Kingdom |pages=117 |oclc= 1255524478|author-link=Rodney Huddleston |author-link2=Geoffrey K. Pullum}} 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 words {{lang|ang|twā}} (feminine), {{lang|ang|tū}} (neuter), and {{lang|ang|twēġen}} (masculine, which survives today in the form twain).{{Cite OED|two, adj., n., and adv.}}

The pronunciation {{IPA|/tuː/}}, like that of who, is due to the labialization of the vowel by the w, which then disappeared before the related sound. The successive stages of pronunciation for the Old English {{lang|ang|twā}} would thus be {{IPA|/twɑː/}}, {{IPA|/twɔː/}}, {{IPA|/twoː/}}, {{IPA|/twuː/}}, and finally {{IPA|/tuː/}}.

Mathematics

An integer is determined to be even if it is divisible by two. When written in base 10, all multiples of 2 will end in 0, 2, 4, 6, or 8;{{Cite OEIS|A005843|The nonnegative even numbers|access-date=2022-12-15}} more generally, in any even base, even numbers will end with an even digit. 2 is the smallest and the only even prime number, and the first Ramanujan prime.{{Cite web |title=Sloane's A104272 : Ramanujan primes |url=https://oeis.org/A104272 |url-status=dead |archive-url=https://web.archive.org/web/20110428165633/https://oeis.org/A104272 |archive-date=2011-04-28 |access-date=2016-06-01 |website=The On-Line Encyclopedia of Integer Sequences |publisher=OEIS Foundation}} It is also the first superior highly composite number,{{Cite web |title=A002201 - OEIS |url=https://oeis.org/A002201 |access-date=2024-11-28 |website=oeis.org}} and the first colossally abundant number.{{Cite web |title=A004490 - OEIS |url=https://oeis.org/A004490 |access-date=2024-11-28 |website=oeis.org}}

= Geometry =

A digon is a polygon with two sides (or edges) and two vertices.{{cite book |last=Wilson |first=Robin |title=Four Colors Suffice |publisher=Princeton University Press |year=2014 |isbn=978-0-691-15822-8 |edition=Revised color}}{{rp|52}} Two distinct points in a plane are always sufficient to define a unique line in a nontrivial Euclidean space.{{Cite book |last=Carrell |first=Jim |url=https://personal.math.ubc.ca/~carrell/307_chap1.pdf |title=MATH 307 Applied Linear Algebra |chapter=Chapter 1 {{!}} Euclidean Spaces and Their Geometry}}

= Set theory =

A set that is a field has a minimum of two elements.{{cite web| url=https://proofwiki.org/wiki/Field_Contains_at_least_2_Elements|title=Field Contains at least 2 Elements}}

Base 2

{{See also|Binary number}}

Binary is a number system with a base of two, it is used extensively in computing.{{Cite web |title=How computers see the world - Binary - KS3 Computer Science Revision |url=https://www.bbc.co.uk/bitesize/guides/z26rcdm/revision/1 |access-date=2024-06-05 |website=BBC Bitesize |language=en-GB}}

List of basic calculations

class="wikitable" style="text-align: center; background: white"

|+

!Multiplication

!1

!2

!3

!4

!5

!6

!7

!8

!9

!10

!11

!12

!13

!14

!15

!16

!17

!18

!19

!20

!21

!22

!23

!24

!25

!50

!100

2 × x

|2

|4

|6

|8

|10

|12

|14

|16

|18

|20

|22

|24

|26

|28

|30

|32

|34

|36

|38

|40

|42

|44

|46

|48

|50

|100

|200

class="wikitable" style="text-align: center; background: white"
width="105px"|Division

!1

!2

!3

!4

!5

!6

!7

!8

!9

!10

!width="5px"|

!11

!12

!13

!14

!15

!16

!17

!18

!19

!20

2 ÷ x

|2

| rowspan="2"|1

|0.{{overline|6}}

|0.5

|0.4

|0.{{overline|3}}

|0.{{overline|285714}}

|0.25

|0.{{overline|2}}

|0.2

!

|0.{{overline|18}}

|0.1{{overline|6}}

|0.{{overline|153846}}

|0.{{overline|142857}}

|0.1{{overline|3}}

|0.125

|0.{{overline|1176470588235294}}

|0.{{overline|1}}

|0.{{overline|105263157894736842}}

|0.1

x ÷ 2

|0.5

|1.5

|2

|2.5

|3

|3.5

|4

|4.5

|5

!

|5.5

|6

|6.5

|7

|7.5

|8

|8.5

|9

|9.5

|10

class="wikitable" style="text-align: center; background: white"
width="105px"|Exponentiation

!1

!2

!3

!4

!5

!6

!7

!8

!9

!10

!width="5px"|

!11

!12

!13

!14

!15

!16

!17

!18

!19

!20

2{{sup|x}}

|2

| rowspan="2" |4

|8

| rowspan="2" |16

|32

|64

|128

|256

|512

|1024

!

|2048

|4096

|8192

|16384

|32768

|65536

|131072

|262144

|524288

|1048576

x{{sup|2}}

|1

|9

|25

|36

|49

|64

|81

|100

!

|121

|144

|169

|196

|225

|256

|289

|324

|361

|400

Evolution of the Arabic digit

Image:Evolution2glyph.png

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 and Japanese languages (and Korean Hanja) still use this method. The Gupta script 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.Georges Ifrah, The Universal History of Numbers: From Prehistory to the Invention of the Computer transl. David Bellos et al. London: The Harvill Press (1998): 393, Fig. 24.62

In science

  • The first magic number - number of electrons in the innermost electron shell of an atom.{{Cite web|url=https://www.sjsu.edu/faculty/watkins/magicnumbers2.htm|title=The Complete Explanation of the Nuclear Magic Numbers Which Indicate the Filling of Nucleonic Shells and the Revelation of Special Numbers Indicating the Filling of Subshells Within Those Shells|website=www.sjsu.edu|access-date=2019-12-22|archive-date=2019-12-02|archive-url=https://web.archive.org/web/20191202130317/http://www.sjsu.edu/faculty/watkins/magicnumbers2.htm|url-status=dead}}

See also

References

{{Reflist}}

External links

{{Portal|Mathematics}}

{{Commons and category|2 (number)|2 (number)}}

  • [http://primes.utm.edu/curios/page.php/2.html Prime curiosities: 2]

{{Wiktionary|two|both}}

{{Integers|zero}}

{{Authority control}}

{{DEFAULTSORT:2 (Number)}}

Category:2 (number)

Category:Integers