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.