twentieth

Twentieth is the ordinal form of the number twenty, used to indicate position in a sequence: the twentieth chapter, the twentieth day, or the twentieth item in a list.

As a noun, a twentieth refers to one of twenty equal parts of a whole, for example a twentieth of a circle, or to fractions expressed as the plural twentieths.

In time and history, the term is often used for the twentieth century, a period roughly from 1901 to 2000 by common convention (some sources use 1900–1999). Phrases such as the Twentieth Amendment of the U.S. Constitution are also encountered, as are references to events or works associated with that era.

Etymology: Twentieth derives from twenty, with the standard English ordinal suffix; the spelling reflects historical pronunciation changes from Old English forms such as twentig to the modern word.