10
10 is the even natural number following 9 and preceding 11. Ten is the base of the decimal numeral system, the most common system of denoting numbers in both spoken and written language.
The number "ten" originates from the Proto-Germanic root "*tehun", which in turn comes from the Proto-Indo-European root "*dekm-", meaning "ten". This root is the source of similar words for "ten" in many other Germanic languages, like Dutch, German, and Swedish. The use of the decimal system is probably because humans have ten fingers and ten toes, which people may have used to count by.
Linguistics
- A collection of ten items is called a decade.
- The ordinal adjective is decimal; the distributive adjective is denary.
- Increasing a quantity by one order of magnitude is most widely understood to mean multiplying the quantity by ten.
- To reduce something by one tenth is to decimate.
Mathematics
- 10 is a composite number and a happy number.
- 10 is the smallest noncototient number.
Decagon
List of basic calculations
| Division | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
| 10 ÷ x | 10 | 5 | 3. | 2.5 | 2 | 1. | 1. | 1.25 | 1. | 1 | 0. | 0.8 | 0. | 0. | 0. |
| x ÷ 10 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 | 0.9 | 1 | 1.1 | 1.2 | 1.3 | 1.4 | 1.5 |
Science
- The metric system is based on the number 10, so converting units is done by adding or removing zeros.
- The 10th element of the periodic table is neon.
- The 10th transition metal is zinc.
Mysticism