Dozen

A dozen (commonly abbreviated doz or dz) is a grouping of twelve.

The dozen may be one of the earliest primitive integer groupings, perhaps because there are approximately a dozen cycles of the Moon, or months, in a cycle of the Sun, or year. Twelve is convenient because it has a maximal number of divisors among the numbers up to its double, a property only true of 1, 2, 6, 12, 60, 360, and 2520.

The use of twelve as a base number, known as the duodecimal system (also as dozenal), originated in Mesopotamia (see also sexagesimal). Twelve dozen (12² = 144) are known as a gross; and twelve gross (12³ = 1,728, the duodecimal 1,000) are called a great gross, a term most often used when shipping or buying items in bulk. A great hundred, also known as a small gross, is 120 or ten dozen. Dozen may also be used to express a moderately large quantity as in "several dozen" (e.g., dozens of people came to the party).

Varying by country, some products are packaged or sold by the dozen, often foodstuff (a dozen eggs).

The English word dozen comes from the old form douzaine, a French word meaning 'a group of twelve' ("Assemblage de choses de même nature au nombre de douze" (translation: A group of twelve things of the same nature), as defined in the eighth edition of the Dictionnaire de l'Académie française). This French word is a derivation from the cardinal numeral douze ('twelve', from Latin duodĕcim) and the collective suffix -aine (from Latin -ēna), a suffix also used to form other words with similar meanings such as quinzaine (a group of fifteen), vingtaine (a group of twenty), centaine (a group of one hundred), etc. These French words have synonymous cognates in Spanish: docena, quincena, veintena, centena, etc. English dozen, French douzaine, Catalan dotzena, Portuguese "dúzia", Persian dowjin "دوجین", Arabic درزن (durzen), Turkish "düzine", Hindi darjan "दर्जन", German Dutzend, Swedish dussin, Dutch dozijn, Italian dozzina and Polish tuzin, are also used as indefinite quantifiers to mean 'about twelve' or 'many' (as in "a dozen times", "dozens of people").

A confusion may arise with the Anglo-Norman dizeyne (French dixaine or dizaine) a tithing, or group of ten households — dating from the earlier English system of grouping households into tens and hundreds for the purposes of law, order and mutual surety (see Tithing). In some texts this 'dizeyne' may be rendered as 'dozen'.

The phrase "half a dozen", also half-dozen or half dozen, means six (6) of something, as 6 is half of 12. The idiom "six of one, half a dozen of the other" means two options are of equal worth so choosing one is the same as choosing the other.

A baker's dozen, devil's dozen, or long dozen is 13, one more than a standard dozen. The broadest use of baker's dozen is simply a group of thirteen objects.