10

10 (ten) 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.

[1] There are exactly 10 small Pisot numbers that do not exceed the golden ratio.

[2] A ten sided polygon is called a decagon.

The metric system is based on the number 10, so converting units is done by adding or removing zeros (e.g. 1 centimetre = 10 millimetres, 1 decimetre = 10 centimetres, 1 meter = 100 centimetres, 1 dekametre = 10 meters, 1 kilometre = 1,000 meters).