U+00AA Feminine Ordinal Indicator

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In written languages, an ordinal indicator is a character, or group of characters, following a numeral denoting that it is an ordinal number, rather than a cardinal number. Historically these letters were "elevated terminals", that is to say the last few letters of the full word denoting the ordinal form of the number displayed as a superscript. Probably originating with Latin scribes, the character(s) used vary in different languages.

In English orthography, this corresponds to the suffixes ‑st, ‑nd, ‑rd, ‑th in written ordinals (represented either on the line 1st, 2nd, 3rd, 4th or as superscript 1^st, 2^nd, 3^rd, 4^th). Also commonly encountered in Romance languages are the superscript or superior (and often underlined) masculine ordinal indicator, º, and feminine ordinal indicator, ª. In formal typography, the ordinal indicators ª and º are distinguishable from other characters.

The practice of underlined (or doubly underlined) superscripted abbreviations was common in 19th-century writing (not limited to ordinal indicators in particular, and extant in the numero sign №), and was found in handwritten English until at least the late 19th century (e.g. first abbreviated '1^st' or 1^st).