Dozen
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A dozen 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 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.