2

← 1 2 3 →
−10123456789→ List of numbers; Integers; ←0102030405060708090→
Cardinal	two
Ordinal	2nd (second)
Numeral system	binary
Factorization	prime
Gaussian integerfactorization
Prime	1st
Divisors	1, 2
Greek numeral	Β´
Roman numeral	II, ii
Greekprefix	di-
Latinprefix	duo-/bi-
Old Englishprefix	twi-
Binary	102
Ternary	23
Senary	26
Octal	28
Duodecimal	212
Hexadecimal	216
Greek numeral	β'
Arabic,Kurdish,Persian,Sindhi,Urdu	٢
Ge'ez	፪
Bengali	২
Chinese numeral	Nhị, nhị, hai
Devanāgarī	२
Telugu	౨
Tamil	௨
Kannada	೨
Hebrew	ב
Armenian	Բ
Khmer	២
Maya numerals	••
Thai	๒
Georgian	Ⴁ/ⴁ/ბ(Bani)
Malayalam	൨
Babylonian numeral	𒐖
Egyptian hieroglyph,Aegean numeral,Chinese counting rod	\|\|
Morse code	.._ _ _

2(two) is anumber,numeralanddigit.It is thenatural numberfollowing1and preceding3.It is the smallest and the only evenprime number.

Because it forms the basis of aduality,it hasreligiousandspiritualsignificance in manycultures.

As a word

Twois most commonly adeterminerused withpluralcountable nouns, as intwo daysorI'll take these two.^[1]Twois anounwhen it refers to the number two as intwo plus two is four.

Etymology oftwo

The wordtwois derived from theOld Englishwordstwā(feminine),tū(neuter), andtwēġen(masculine, which survives today in the formtwain).^[2]

The pronunciation/tuː/,like that ofwhois due to thelabializationof the vowel by thew,which then disappeared before the related sound. The successive stages of pronunciation for the Old Englishtwāwould thus be/twɑː/,/twɔː/,/twoː/,/twuː/,and finally/tuː/.^[2]

Mathematics

Anintegeris determined to beevenif it isdivisibleby two. When written in base 10, allmultiplesof 2 will end in0,2, 4, 6, or8.^[3]2 is the smallest and the only evenprime number,and the firstRamanujan prime.^[4]It is also the firstsuperior highly composite number,^[5]and the firstcolossally abundant number.^[6]

Geometry

Adigonis a polygon with two sides (oredges) and twovertices.^[7]^: 52Two distinctpointsin aplaneare alwayssufficientto define a uniquelinein a nontrivialEuclidean space.^[8]

Set theory

Asetthat is afieldhas a minimum of twoelements.^[9]ACantor spaceis atopological space $2^{\mathbb {N} }$ homeomorphicto theCantor set.^{[citation needed]}

Base 2

Binaryis a number system with abaseof two, it is used extensively incomputing.^[10]

List of basic calculations


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

Division	1	2	3	4	5	6	7	8	9	10		11	12	13	14	15	16	17	18	19	20
2 ÷x	2	1	0.6	0.5	0.4	0.3	0.285714	0.25	0.2	0.2		0.18	0.16	0.153846	0.142857	0.13	0.125	0.1176470588235294	0.1	0.105263157894736842	0.1
x÷ 2	0.5	1	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

Exponentiation	1	2	3	4	5	6	7	8	9	10		11	12	13	14	15	16	17	18	19	20
2^x	2	4	8	16	32	64	128	256	512	1024		2048	4096	8192	16384	32768	65536	131072	262144	524288	1048576
x²	1	4	9	16	25	36	49	64	81	100		121	144	169	196	225	256	289	324	361	400

Evolution of the Arabic digit

The digit used in the modern Western world to represent the number 2 traces its roots back to the IndicBrahmic script,where "2" was written as two horizontal lines. The modernChineseandJapaneselanguages (and KoreanHanja) still use this method. TheGupta scriptrotated 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 theNagariscript, the top line was written more like a curve connecting to the bottom line. In the ArabicGhubarwriting, 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.^[11]

In fonts withtext figures,digit 2 usually is ofx-height,for example,.^{[citation needed]}

In science

The firstmagic number.^[12]

References

^Huddleston, Rodney D.;Pullum, Geoffrey K.;Reynolds, Brett (2022).A student's introduction to English grammar(2nd ed.). Cambridge, United Kingdom:Cambridge University Press.p. 117.ISBN 978-1-316-51464-1.OCLC 1255524478.
^^a ^b"two, adj., n., and adv.".Oxford English Dictionary(Online ed.).Oxford University Press.(Subscription orparticipating institution membershiprequired.)
^Sloane, N. J. A.(ed.)."Sequence A005843 (The nonnegative even numbers)".TheOn-Line Encyclopedia of Integer Sequences.OEIS Foundation.Retrieved2022-12-15.
^"Sloane's A104272: Ramanujan primes".The On-Line Encyclopedia of Integer Sequences.OEIS Foundation. Archived fromthe originalon 2011-04-28.Retrieved2016-06-01.
^"A002201 - OEIS".oeis.org.Retrieved2024-11-28.
^"A004490 - OEIS".oeis.org.Retrieved2024-11-28.
^Wilson, Robin (2014).Four Colors Suffice(Revised color ed.). Princeton University Press.ISBN 978-0-691-15822-8.
^Carrell, Jim. "Chapter 1 | Euclidean Spaces and Their Geometry".MATH 307 Applied Linear Algebra(PDF).
^"Field Contains at least 2 Elements".
^"How computers see the world - Binary - KS3 Computer Science Revision".BBC Bitesize.Retrieved2024-06-05.
^Georges Ifrah,The Universal History of Numbers: From Prehistory to the Invention of the Computertransl. David Bellos et al. London: The Harvill Press (1998): 393, Fig. 24.62
^"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".sjsu.edu.Archived fromthe originalon 2019-12-02.Retrieved2019-12-22.

External links

Prime curiosities: 2

[1] Huddleston, Rodney D.;Pullum, Geoffrey K.;Reynolds, Brett (2022).A student's introduction to English grammar(2nd ed.). Cambridge, United Kingdom:Cambridge University Press.p. 117.ISBN 978-1-316-51464-1.OCLC 1255524478.

[OED-2] "two, adj., n., and adv.".Oxford English Dictionary(Online ed.).Oxford University Press.(Subscription orparticipating institution membershiprequired.)

[3] Sloane, N. J. A.(ed.)."Sequence A005843 (The nonnegative even numbers)".TheOn-Line Encyclopedia of Integer Sequences.OEIS Foundation.Retrieved2022-12-15.

[4] "Sloane's A104272: Ramanujan primes".The On-Line Encyclopedia of Integer Sequences.OEIS Foundation. Archived fromthe originalon 2011-04-28.Retrieved2016-06-01.

[5] "A002201 - OEIS".oeis.org.Retrieved2024-11-28.

[6] "A004490 - OEIS".oeis.org.Retrieved2024-11-28.

[Wilson2014-7] Wilson, Robin (2014).Four Colors Suffice(Revised color ed.). Princeton University Press.ISBN 978-0-691-15822-8.

[8] Carrell, Jim. "Chapter 1 | Euclidean Spaces and Their Geometry".MATH 307 Applied Linear Algebra(PDF).

[9] "Field Contains at least 2 Elements".

[10] "How computers see the world - Binary - KS3 Computer Science Revision".BBC Bitesize.Retrieved2024-06-05.

[11] Georges Ifrah,The Universal History of Numbers: From Prehistory to the Invention of the Computertransl. David Bellos et al. London: The Harvill Press (1998): 393, Fig. 24.62

[12] "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".sjsu.edu.Archived fromthe originalon 2019-12-02.Retrieved2019-12-22.

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