12 (number)
From Wikipedia, the free encyclopedia.
12 (twelve) is the natural number following 11 and preceding 13.
| |||
|---|---|---|---|
| Cardinal | twelve | ||
| Ordinal | twelfth | ||
| Numeral system | duodecimal | ||
| Factorization | |||
| Roman numeral | XII | ||
| Binary | 1100 | ||
| Hexadecimal | C | ||
In mathematics
Twelve is a composite number, its proper divisors being 1, 2, 3, 4 and 6. Twelve is also a highly composite number, the next one being 24.
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.
A twelve-sided polygon is a dodecagon. A twelve-sided polyhedron is a dodecahedron. Twelve is a pentagonal number.
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 loaves in a baker's dozen.) The duodecimal system (1210 [twelve] = 1012), which is the use of 12 as a division factor for many historical weights and measures, including hours, probably originates from Mesopotamia. See also: base 12. As Schoolhouse Rock explains in its song "Little Twelvetoes", if humankind had been born with twelve fingers, they would have counted and multiplied using the duodecimal system. (There is no need to have twelve fingers though, since one will easily arrive at the duodecimal system by simply counting the phalanx of fingers with the same hand's thumb, a practice in use with some people until the present day.) In base thirteen and higher bases (such as hexadecimal), twelve is represented as C.
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]", thus strongly indicating the use of a duodecimal system.
In time
There are twelve months in a year.
The Western zodiac has twelve signs, as does the Chinese zodiac.
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 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.
The minute hand of a clock face turns twelve times faster than the hour hand.
In other fields
In English, twelve is the number of greatest magnitude that has just one syllable.
There are normally twelve pairs of ribs in the human body.
The 12th moon of Jupiter is Lysithea.
Jewish tradition and the old testament of the Bible talks of twelve tribes of Israel. The new testament of the Bible describes twelve apostles of Jesus Christ. The Book of Revelation 12:1 mentions a woman - usually interpreted as Virgin Mary - wearing a crown of twelve stars.
Twelve stars are also featured on the European flag.
In modern Jewish practice, girls get their bat mitzvah on the Shabbat after their twelfth birthdays.
In the United States, twelve people are appointed to sit on a jury for felony trials in all but four states, and in federal and D.C courts. The number of jurors in the movie gave the title to the film 12 Angry Men.
Other movies with the number twelve in their titles include The Dirty Dozen, 12 Monkeys and Twelve Chairs.
The song Twelve Days of Christmas came from the traditional practice of extending Yuletide celebrations over the twelve days from Christmas to Epiphany.
Twelfth Night, another name for the 12th Day of Christmas or January 6, gives its name to a Shakespeare comedy, as well as that of progressive rock band; see Twelfth Night (band).
Twelve is:
- The atomic number of magnesium.
- ASCII and Unicode code point for form feed.
- In music, the number of pitch classes in an octave, not counting the duplicated (octave) pitch. Also, the total number of major keys, (not counting enharmonic equivalents) and the total number of minor keys (also not counting equivalents). This applies only to twelve tone equal temperament, the most common tuning used today in western influenced music.
- The designation of United States Interstate 12, a freeway in Louisiana.
- a video game character. See Twelve (video game character)
- Historical years: 12 A.D., 12 B.C, or 1912