fifteenth

Fifteenth is the ordinal form of the number fifteen, used to indicate a position in a sequence. It is formed by adding the suffix -th to the cardinal fifteen, following a regular pattern for English ordinals. The term can function as an adjective or a noun in phrases such as “the fifteenth item” or “the fifteenth day,” and is commonly used in dating, sequencing, lists, rankings, and legal or historical references.

In practical use, fifteenth appears in dates (for example, the fifteenth of March), in enumerations (the fifteenth entry in a document), and in mathematical contexts where fractions are expressed as one fifteenth (1/15). In music theory, the term can refer to the interval spanning two octaves, though this usage is less common and often described more simply as a two-octave interval.

A notable historical usage is the Fifteenth Amendment to the United States Constitution, ratified in 1870. This amendment prohibits denying a citizen the right to vote on the basis of race, color, or previous condition of servitude, and it is one of the key Reconstruction-era amendments that followed the Civil War.

Etymology generally traces the form directly to the cardinal number fifteen plus the standard English ordinal suffix -th, with the same pattern extending to other ordinals. The word is routinely found in dictionaries, encyclopedias, and general written language as a standard ordinal designation.