Why is it 21st and not 21th?

The suffix follows how the word ends when spoken. Twenty-first ends in first, so it takes -st. The pattern repeats for any number ending in 1, 2, or 3, except the teens 11, 12, and 13, which all take -th.

Do ordinals change with gender in some languages?

Yes. In Spanish and Portuguese, primero becomes primera before a feminine noun; Italian and French agree too. English does not inflect ordinals, so first stays first regardless.

How do I write ordinals in dates?

English often uses ordinals in dates (July 4th), though the digit alone is fine in formal writing. Many other languages use a cardinal for most days and reserve the ordinal for the first of the month, so conventions vary.

Is zero an ordinal number?

In everyday counting, no — ordinals start at first. Some technical contexts like computer indexing use a zeroth position, but that is a specialist convention rather than standard language.

Ordinal Numbers Explained: 1st, 2nd, 3rd

Published 11/13/2025 · 2 min read · Everyday calculators

Lena Hoffmann — Science & education writer at OneKitly

Mathematics · Physics

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In short

An ordinal number names a position in an order — first, second, third — while a cardinal number names a quantity — one, two, three. In English you usually add -th to the cardinal (four to fourth), with first, second, and third as exceptions. Every language builds ordinals its own way, so the endings and abbreviations differ from one to the next.

Ordinal numbers show position, cardinal numbers show quantity. Learn the difference and how each language forms ordinals differently.

Cardinal versus ordinal

Cardinal numbers answer how many: three apples, ten runners, one house. Ordinal numbers answer which position: the third apple, the tenth runner, the first house. Every cardinal has a matching ordinal, and the pair carries different information — a count versus a rank.

In English writing, ordinals appear as a numeral plus a two-letter suffix: 1st, 2nd, 3rd, then -th from 4th onward. The suffix follows the pronunciation, which is why 21st, 22nd, and 23rd repeat the first, second, third pattern while 11th, 12th, and 13th all take -th.

How each language forms ordinals

The rules diverge quickly. English adds -th (with first, second, third as exceptions). French adds -ième (deuxième), keeping premier for one. Spanish and Portuguese use dedicated forms (primero, segundo) that agree in gender and number. German appends -te or -ste and marks the abbreviation with a period (4.). Italian has unique words up to tenth, then adds -esimo.

Where ordinals show up

Ordinals appear in dates, rankings, floors of a building, chapter numbers, and race results. Because their form depends on the language and often on gender, translating them is not just a matter of swapping the numeral — the second floor, la deuxième, el segundo, and der zweite all differ. A converter that knows each language's rules removes the guesswork.

Ordinal number converterConvert numbers into English ordinals (1st, 2nd, 3rd…).Try the tool →

Frequently asked questions

Why is it 21st and not 21th?: The suffix follows how the word ends when spoken. Twenty-first ends in first, so it takes -st. The pattern repeats for any number ending in 1, 2, or 3, except the teens 11, 12, and 13, which all take -th.
Do ordinals change with gender in some languages?: Yes. In Spanish and Portuguese, primero becomes primera before a feminine noun; Italian and French agree too. English does not inflect ordinals, so first stays first regardless.
How do I write ordinals in dates?: English often uses ordinals in dates (July 4th), though the digit alone is fine in formal writing. Many other languages use a cardinal for most days and reserve the ordinal for the first of the month, so conventions vary.
Is zero an ordinal number?: In everyday counting, no — ordinals start at first. Some technical contexts like computer indexing use a zeroth position, but that is a specialist convention rather than standard language.

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