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In [[curling]], the House or the circular scoring area, is 12 feet in diameter.
In [[curling]], the House or the circular scoring area, is 12 feet in diameter.

In fantasy football - Nick Portnoy's draft pick!


==In technology==
==In technology==

Revision as of 12:42, 26 August 2010

← 11 12 13 →
Cardinaltwelve
Ordinalth
Numeral systemduodecimal
Factorization
Divisors1, 2, 3, 4, 6, 12
Greek numeralΙΒ´
Roman numeralXII
Latin prefixduodeca-
Binary11002
Ternary1103
Senary206
Octal148
Duodecimal1012
HexadecimalC16
Mathematical properties
φ(12) = 4 τ(12) = 6
σ(12) = 28 π(12) = 5
μ(12) = 0 M(12) = -2

12 (twelve) (Template:Pron-en) is the natural number following 11 and preceding 13.

The word "twelve" is a native English word that presumably arises from the Germanic compound twa-lif "two-leave", meaning that two is left after one takes away the base, ten. This compound meaning may have been transparent to speakers of Old English, but the modern form "twelve" is quite opaque. Only the remaining tw- hints that twelve and two are related. Etymology (Weekley, Skeat) suggests that "twelve" (similar to "eleven") consists of two parts, the first meaning "two" and the second "leftover", so a literal translation would yield "two remaining [after having ten taken]".

A group of twelve things is called a Duodecad. The ordinal adjective is duodenary, twelfth. The adjective referring to a group consisting of twelve things is duodecuple.

The number twelve is often used as a sales unit in trade, and is often referred to as a dozen. Twelve dozen are known as a gross. (Note that there are thirteen items in a baker's dozen.)

As shown below, the number twelve is frequently cited in the Abrahamic religions and is also central to Western calendar and units of time.

In mathematics

Twelve is a composite number, the smallest number with exactly six divisors, its proper divisors being 1, 2, 3, 4, and 6. Twelve is also a highly composite number, the next one being 24. It is the first composite number of the form p2q; a square-prime, and also the first member of the (p2) family in this form. 12 has an aliquot sum of 16 (133% in abundance). Accordingly, 12 is the first abundant number (in fact a superabundant number) and demonstrates an 8 member aliquot sequence; {12,16,15,9,4,3,1,0} 12 is the 3rd composite number in the 3-aliquot tree. The only number which has 12 as its aliquot sum is the square 121. Only 2 other square primes are abundant (18 and 20).

Twelve is a sublime number, a number that has a perfect number of divisors, and the sum of its divisors is also a perfect number. Since there is a subset of 12's proper divisors that add up to 12 (all of them but with 4 excluded), 12 is a semiperfect number.

If an odd perfect number is of the form 12k + 1, it has at least twelve distinct prime factors.

Twelve is a superfactorial, being the product of the first three factorials. Twelve being the product of three and four, the first four positive integers show up in the equation 12 = 3 × 4, which can be continued with the equation 56 = 7 × 8.

Twelve is the ninth Perrin number, preceded in the sequence by 5, 7, 10, and also appears in the Padovan sequence, preceded by the terms 5, 7, 9 (it is the sum of the first two of these). It is the fourth Pell number, preceded in the sequence by 2 and 5 (it is the sum of the former plus twice the latter).

A twelve-sided polygon is a dodecagon. A twelve-faced polyhedron is a dodecahedron. Regular cubes and octahedrons both have 12 edges, while regular icosahedrons have 12 vertices. Twelve is a pentagonal number. The densest three-dimensional lattice sphere packing has each sphere touching 12 others, and this is almost certainly true for any arrangement of spheres (the Kepler conjecture). Twelve is also the kissing number in three dimensions.

Twelve is the smallest weight for which a cusp form exists. This cusp form is the discriminant Δ(q) whose Fourier coefficients are given by the Ramanujan τ-function and which is (up to a constant multiplier) the 24th power of the Dedekind eta function. This fact is related to a constellation of interesting appearances of the number twelve in mathematics ranging from the value of the Riemann zeta function function at -1 i.e. ζ(-1)=-1/12, the fact that the abelianization of SL(2,Z) has twelve elements, and even the properties of lattice polygons.

There are twelve Jacobian elliptic functions and twelve cubic distance-transitive graphs.

The duodecimal system (1210 [twelve] = 1012), which is the use of 12 as a division factor for many ancient and medieval weights and measures, including hours, probably originates from Mesopotamia.

In base thirteen and higher bases (such as hexadecimal), twelve is represented as C. In base 10, the number 12 is a Harshad number.

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 25 50 100 1000
12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 204 216 228 240 252 264 300 600 1200 12000


Exponentiation 1 2 3 4 5 6 7 8 9 10 11 12 13
12 144 1728 20736 248832 2985984 35831808 429981696 5159780352 61917364224 743008370688 8916100448256 106993205379072
1 4096 531441 16777216 244140625 2176782336 13841287201 68719476736 282429536481 1000000000000 3138428376721 8916100448256 23298085122481

In numeral systems

١٢ Arabic ԺԲ Armenian
ιβʹ Ionian Greek ΔΙΙ Attic Greek
יב Hebrew
V20Z1Z1
Egyptian
१२ Indian (Devanāgarī) 十二 Chinese and Japanese
௧௨ Tamil Roman and Etruscan
๑๒ Thai IIX Chuvash

In science

Astronomy

In religion

The number 12 is very important in many religions, mainly Judaism and Christianity, but some uses are to be found in pagan times.

In Antiquity there are numerous magical/religious uses of twelves.[1] Ancient Greek religion, the Twelve Olympians were the principal gods of the pantheon. The chief Norse god, Odin, had 12 sons. Several sets of twelve cities are identified in history as a dodecapolis, the most familiar being the Etruscan League. In the King Arthur Legend, Arthur is said to have subdued 12 rebel princes and to have won 12 great battles against Saxon invaders. [source: Benet's Reader's Encyclopedia, 3d ed]

The importance of 12 in Judaism and Christianity can be found in the Bible. The biblical Jacob had 12 sons, who were the progenitors of the Twelve Tribes of Israel, while the New Testament describes twelve apostles of Jesus; when Judas Iscariot was disgraced, a meeting was held (Acts) to add Matthias to complete the number twelve once more. (Today, The Church of Jesus Christ of Latter-day Saints has a Quorum of the Twelve Apostles.)

The Book of Revelation contains much numerical symbolism, and a lot of the numbers mentioned have 12 as a divisor. 12:1 mentions a woman — interpreted as the people of Israel, the Church or the Virgin Mary — wearing a crown of twelve stars (representing each of the twelve tribes of Israel). Furthermore, there are 12,000 people sealed from each of the twelve tribes of Israel, making a total of 144,000 (which is the square of 12 multiplied by a thousand).

There are 12 days of Christmas. The song Twelve Days of Christmas came from the traditional practice of extending Yuletide celebrations over the twelve days from Christmas day to the eve of Epiphany; the period of thirteen days including Epiphany is sometimes known as Christmastide. Thus Twelfth Night is another name for the twelfth day of Christmas or January 5 (the eve of Epiphany). Similarly, Eastern Orthodoxy observes 12 Great Feasts.

In Shi'a Islam, there are twelve Imams, legitimate successors of the prophet Muhammad. These twelve early leaders of Islam are—Ali, Hasan, Husayn, and nine of Husayn's descendants.

In Hinduism, the sun god Surya has 12 names. Also, there are 12 Petals in Anahata(Heart Chakra.)

In time

  • Most calendar systems have twelve months in a year.
  • The Western zodiac has twelve signs, as does the Chinese zodiac.
  • The Chinese use a 12 years cycle for time-reckoning called Earthly Branches.
  • There are twenty-four hours in a day in all, with twelve hours for a half a day. The hours are numbered from one to twelve for both the ante meridiem (a.m.) half of the day and the post meridiem (p.m.) half of the day. 12:00 after a.m. and before p.m. (in the middle of the day) is midday or noon, and 12:00 after p.m. and before a.m. (in the middle of the night) is midnight. A new day is considered to start with the stroke of midnight. Furthermore, the basic units of time (60 seconds, 60 minutes, 24 hours) can all perfectly divide by twelve.

Age 12

In sports

In rugby union one of the centres, most often but not always the inside centre, wears the 12 shirt, while in rugby league, one of the second-row forwards wears the number 12 jersey.

In both soccer and American Football, the number 12 can be a symbolic reference to the fans because of the support they give to the 11 players on the field. Texas A&M University reserves the number 12 jersey for a walk on player who represents the original "12th Man", a fan who was asked to play when the team's reserves were low in a college American football game in 1922. Similarly, Bayern Munich, Hammarby, Feyenoord, Atlético Mineiro, Flamengo and the Seattle Seahawks do not allow field players to wear the number 12 on their jersey because it is reserved for their supporters.

In the Canadian Football League (CFL) 12 is the maximum number of players that can be on the field of play for each team at any time.

In ten-pin bowling, 12 is the number of strikes needed for a perfect game.

In curling, the House or the circular scoring area, is 12 feet in diameter.

In fantasy football - Nick Portnoy's draft pick!

In technology

In the arts

Film

Movies with the number twelve or its variations in their titles include

Television

Theatre

Literature

Music

Art Theory

  • There are twelve basic hues in the color wheel; 3 primary colors (red, yellow, blue), 3 secondary colors (orange, green & purple) and 6 tertiary colors (names for these vary, but are intermediates between the primaries and secondaries).

Games

  • The Roman form of 12 (XII) is used as the symbol of the organization MJ12 in the Deus Ex computer game.

In other fields

12 stars are featured on the Flag of Europe

Historical years

12 A.D., 12 B.C., 1912, 2012, etc.

See also

Notes

  1. ^ The classic assembly of instances is Th. Weinreich, "Zwölfgötten' in W.H. Roscher, Ausfurliches Lexikon der Griechischen und Römishen Mythologie vol. vi. col. 764-848, noted in Robert Drews, "Light from Anatolia on the Roman Fasces"The American Journal of Philology 93.1 (January 1972) pp. 40-51) p 43 note 10. The twelve lictors carried fasces of twelve rods.

References

  • Schwartzman, Steven (1994). The words of mathematics: An etymological dictionary of mathematical terms used in English. The Mathematical Association of America. ISBN 0-88385-511-9.
  • Lattice Polygons and the Number 12, Bjorn Poonen, Fernando Rodriguez-Villegas, American Mathematical Monthly, Vol. 107, No. 3 (Mar., 2000) , pp. 238–250 [1]

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