Ordinal indicator

◌ª | ◌º
◌ª \| ◌º
Ordinal indicator ; (feminine \| masculine)
In Unicode	U+00AA ª FEMININE ORDINAL INDICATOR (ª); U+00BA º MASCULINE ORDINAL INDICATOR (º);
Different from
Different from	U+00B0 ° DEGREE SIGN; U+02DA ˚ RING ABOVE U+030A ◌̊ COMBINING RING ABOVE; U+1D52 ᵒ MODIFIER LETTER SMALL O; U+1D3C ᴼ MODIFIER LETTER CAPITAL O; U+2070 ⁰ SUPERSCRIPT ZERO; U+1D43 ᵃ MODIFIER LETTER SMALL A;

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. 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 are the superscript or superior (and often underlined) masculine ordinal indicator, º, and feminine ordinal indicator, ª, originally from Romance and then via the cultural influence of Italian, as in 1º primo and 1ª prima. In correct typography, the ordinal indicators ª and º should be distinguishable from other characters.^[1]

The practice of underlined (or doubly underlined) superscripted abbreviations was common in 19th-century writing (not limited to ordinal indicators in particular, and also extant in the numero sign №), and was also found in handwritten English until at least the late 19th century (e.g. first abbreviated '1^st' or 1^st).^[2]

^ "Microsoft typography — Character design standards". Microsoft Corporation. 9 June 2022. Note: Traditionally in Portuguese the ordinal characters should contain the underline. The underline helps avoid confusion between the masculine ordinal and the degree character. This is important at low resolution, such as the screen, when both characters are very similar in size and shape.
^ Max Harold Fisch; Christian J. W. Kloesel (1989). "Essay on the Editorial Method". Writings of Charles S. Peirce: 1879–1884. Vol. 4. p. 629. ISBN 9780253372017. Peirce also regularly used the nineteenth-century calligraphic convention of double underlining superscript portions of abbreviations such as M^r or 1^st.

[mstyp-1] "Microsoft typography — Character design standards". Microsoft Corporation. 9 June 2022. Note: Traditionally in Portuguese the ordinal characters should contain the underline. The underline helps avoid confusion between the masculine ordinal and the degree character. This is important at low resolution, such as the screen, when both characters are very similar in size and shape.

[2] Max Harold Fisch; Christian J. W. Kloesel (1989). "Essay on the Editorial Method". Writings of Charles S. Peirce: 1879–1884. Vol. 4. p. 629. ISBN 9780253372017. Peirce also regularly used the nineteenth-century calligraphic convention of double underlining superscript portions of abbreviations such as M^r or 1^st.

[1]

[2]

◌ª \| ◌º
Ordinal indicator (feminine \| masculine)
In Unicode	U+00AA ª FEMININE ORDINAL INDICATOR (ª) U+00BA º MASCULINE ORDINAL INDICATOR (º)
Different from
Different from	U+00B0 ° DEGREE SIGN U+02DA ˚ RING ABOVE U+030A ◌̊ COMBINING RING ABOVE U+1D52 ᵒ MODIFIER LETTER SMALL O U+1D3C ᴼ MODIFIER LETTER CAPITAL O U+2070 ⁰ SUPERSCRIPT ZERO U+1D43 ᵃ MODIFIER LETTER SMALL A