The building blocks of English

Affixes

duodeci-

Twelve; twelfth.

Latin duodecim, twelve; duodecimo, twelfth.

This form appears relatively rarely, the Greek dodeca‑ being more common. Examples include duodecimal, of a system of counting or numerical notation that has twelve as a base; duodecimo, a size of book in which each leaf is one twelfth of the size of the printing sheet; duodecennial, relating to a period of twelve years; duodecad (rarely duodecade), either a group of twelve or a period of twelve years.