10 (ten) is the natural number following 9 and preceding 11. Prefixes for 10 include deca (Greek) and deci (Latin).
In mathematics
Ten is a composite number, its proper divisors being 1, 2 and 5.
Ten is the base of the decimal numeral system, by far the most common system of denoting numbers in both spoken and written language. Any integer written in the decimal system can be multiplied by ten by adding a zero to the end (eg 855 * 10 = 8550). The reason for the choice of ten is assumed to be that humans have ten fingers (digits).
The Roman numeral for ten is X (which looks like two V's [the Roman numeral for 5] put together); it is thought that the V for five is derived from an open hand (five digits displayed).
The Chinese word numeral for ten is 十, which resembles a cross.
A collection of ten items (most often ten years) is called a decade.
Ten is the sum of the first three prime numbers.
A polygon with ten sides is a decagon, and 10 is a decagonal number. But it is also a triangular number and a centered triangular number.
Ten is the smallest noncototient, a number that can not be expressed as the difference between any integer and the total of coprimes below it.
Ten is a Harshad number and a semimeandric number.
Ten is the number of nQueens Problem solutions for n = 5.
In numeral systems
In science
In astronomy,

Messier object M10, a magnitude 7.5 globular cluster in the constellation Ophiuchus.

The New General Catalogue object http://www.ngcic.org/ NGC 10 , a magnitude 12.5 spiral galaxy in the constellation Sculptor

The Saros number http://sunearth.gsfc.nasa.gov/eclipse/LEsaros/LEsaros1175.html of the solar eclipse series which began on 2467 February 28 and ended on 1169 April 18. The duration of Saros series 10 was 1298.1 years, and it contained 73 solar eclipses.

The Saros number http://sunearth.gsfc.nasa.gov/eclipse/LEsaros/LEsaros1175.html of the lunar eclipse series which began on 2454 June 17 and ended on 1138 August 15. The duration of Saros series 10 was 1316.2 years, and it contained 74 lunar eclipses.
In other fields
A decapod crustacean has ten limbs.
To reduce something by one tenth is to decimate. (In ancient Rome, the killing of one in ten soldiers was the punishment for mutiny.)
There are ten cents in a U.S. or Canadian dime, itself one tenth of a dollar. The word was shortened from decime.
In chess, each side can promote all eight pawns to have a total of ten bishops, knights, or rooks.
People were traditionally tithed one tenth of their produce.
It takes ten to make a minyan.
With ten being the base of the decimal system, a scale of 1 to 10 is often used to rank things, as a smaller version of a 1to100 scale (as is used in percentages and winetasting).
Blake Edwards' 1979 movie 10 http://imdb.com/title/tt0078721/ .
Something that scores perfectly is "a perfect ten". A person who is attractive and physically flawless is often said to be "a ten", from the idea of ranking that person's appearance and sexappeal on a 1to10 scale. E.g. In the movie 10 (movie)10 Bo Derek is supposedly a "10" on that scale.
Counting from one to ten before speaking is often done in order to cool one's temper.
Driving a racing car at tentenths is driving as fast as possible, on the limit.
Ten is:
Last updated: 02082005 13:28:49
Last updated: 05032005 17:50:55