In linguistics, ordinal numerals or ordinal number words are words representing position or rank in a sequential order; the order may be of size, importance, chronology, and so on (e.g., "third", "tertiary"). They differ from cardinal numerals, which represent quantity (e.g., "three") and other types of numerals.

In traditional grammar, all numerals, including ordinal numerals, are grouped into a separate part of speech (Latin: nomen numerale, hence, "noun numeral" in older English grammar books). However, in modern interpretations of English grammar, ordinal numerals are usually conflated with adjectives.

Ordinal numbers may be written in English with numerals and letter suffixes: 1st, 2nd or 2d, 3rd or 3d, 4th, 11th, 21st, 101st, 477th, etc., with the suffix acting as an ordinal indicator. Written dates often omit the suffix, although it is nevertheless pronounced. For example: 5 November 1605 (pronounced "the fifth of November ... "); November 5, 1605, ("November (the) Fifth ..."). When written out in full with "of", however, the suffix is retained: the 5th of November. In other languages, different ordinal indicators are used to write ordinal numbers.

In American Sign Language, the ordinal numbers first through ninth are formed with handshapes similar to those for the corresponding cardinal numbers with the addition of a small twist of the wrist.