Dozen

A "dozen" (commonly abbreviated doz or dz) is a unit of measurement. It means twelve (12) items of something. The term goes back to duodecim, which means 12 in  Latin. Humans might have started to count on a base 12 because there are approximately 12 cycles of the moon in one cycle of the sun. In other words, a solar year has 12 months. The first to have used the unit were probably the Mesopotamians.

12 dozen  (144 items) are a gross. 12 gross (1728 items) are called a great gross. 
A great hundred is 120 or ten dozen (a dozen for each finger on both hands).

The dozen is convenient because its multipliers and multiples are convenient: 12 = 3 × 2 × 2, and 360 = 30 × 12. The French word douzaine means "about twelve" and is part of a family of words with similar meanings, e.g. vingtaine – "about 20"  centaine – "about 100"  etc. A baker's dozen, also known as a long dozen, is thirteen.

Examples:

I have a dozen doughnuts 

There is a dozen members in a team

Category:Numbers