3rd

3rd is the written abbreviation for the ordinal number third, used to indicate position in a sequence, ranking, or order. In English, ordinals are typically formed by adding a suffix to the base numeral: -st for numbers ending in 1, -nd for those ending in 2, -rd for those ending in 3, and -th for all other endings. A standard exception applies to numbers ending in 11, 12, or 13, which use -th regardless of their final digit. Thus examples include 1st, 2nd, 3rd, 4th, as well as 11th, 12th, 13th; 23rd and 103rd are correct under the general rule, while 113th uses -th because it ends with 13.

In practice, 3rd appears in a wide range of contexts. It designates the third item in a list, the third position in a competition, or the third street, avenue, or district in an address (for example, 3rd Street). It is also used in formal references to constitutional, legal, and organizational designations, such as the 3rd Amendment or the 3rd Circuit Court of Appeals. In scientific and mathematical writing, it can denote ordinal sequencing, such as the 3rd element in a sequence, though numerals are often written simply as 3a, 3b, or with superscripts in formal notation.

Etymology traces the word third to Old English thrīd, thrīþa, from Proto-Germanic roots meaning “third.” The suffix -rd in 3rd reflects the English system of ordinal indicators, adapted over many centuries to accommodate numerals in running text and formal references. See also third.

See also: ordinal, ordinal indicator, English numerals.