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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.
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Cardinal | two | |||
Ordinal | 2nd (second / twoth) | |||
Numeral system | binary | |||
Factorization | prime | |||
Gaussian integer factorization | ||||
Prime | 1st | |||
Divisors | 1, 2 | |||
Greek numeral | Β´ | |||
Roman numeral | II, ii | |||
Greek prefix | di- | |||
Latin prefix | duo-/bi- | |||
Old English prefix | 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 | 二,弍,貳 | |||
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 | .._ _ _ |
In mathematics
- An even number is an integer that is divisible by two.
- 2 is the smallest, and the only even prime number.
- Twin primes are primes separated from another prime by 2. There are an infinite number of 2 primes.
- The trivial field has two elements.
- A cantor space is the countable Cartesian product of a set with two elements, it is thus denoted .
- More generally, for any set , its power set can be denoted , representing the (not necessarily countable) Cartesian product of sets containing individual elements of , and the empty set. .
- Powers of two form the basis of binary, which is also used in computer science.
- The row sums of Pascal's triangle sum to successive powers of 2.
- The sum of the reciprocal powers of 2 approaches 2. Equivalently,
Simple Calculations
Multiplication | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 20 | 25 | 50 | 100 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2 × x | 2 | 4 | 6 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | 40 | 50 | 100 | 200 |
Division | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
---|---|---|---|---|---|---|---|---|---|---|
2 ÷ x | 2 | 1 | 0.6 | 0.5 | 0.4 | 0.3 | 0.285714 | 0.25 | 0.2 | 0.2 |
x ÷ 2 | 0.5 | 1.5 | 2 | 2.5 | 3 | 3.5 | 4 | 4.5 | 5 |
Exponentiation | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2x | 2 | 4 | 8 | 16 | 32 | 64 | 128 | 256 | 512 | 1024 | 2048 | 4096 | 8192 | 16384 | 32768 | 65536 | 131072 | 262144 | 524288 | 1048576 |
x2 | 1 | 9 | 25 | 36 | 49 | 64 | 81 | 100 | 121 | 144 | 169 | 196 | 225 | 256 | 289 | 324 | 361 | 400 |
In linguistics
Two is most commonly a determiner used with plural countable nouns, as in two days or I'll take these two.[1] 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 twā (feminine), tū (neuter), and twēġen (masculine, which survives today in the form twain).[2]
The pronunciation /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 twā would thus be /twɑː/, /twɔː/, /twoː/, /twuː/, and finally /tuː/.[2]
Numeral shape
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.[3]
In fonts with text figures, digit 2 usually is of x-height, for example, .[citation needed]
In science
- The number of polynucleotide strands in a DNA double helix.[4]
- The first magic number.[5]
- The atomic number of helium.[6]
See also
Notes
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 or participating institution membership required.)
- ^ 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
- ^ "Double-stranded DNA". Scitable. Nature Education. Archived from the original on 2020-07-24. Retrieved 2019-12-22.
- ^ "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". www.sjsu.edu. Archived from the original on 2019-12-02. Retrieved 2019-12-22.
- ^ Bezdenezhnyi, V. P. (2004). "Nuclear Isotopes and Magic Numbers". Odessa Astronomical Publications. 17: 11. Bibcode:2004OAP....17...11B.