Base-10 integers, when used as adjectives to express order, add a "st", "nd", "rd", and "th" suffix to whatever the number is, depending on whether the ones digit is a 1, 2, 3, or anything else, respectively. The only exceptions are those ending in 11, 12, and 13, which take "th". Why is there an exception for 11, 12, and 13? You can't tell me that "thirteenth" is less awkward than "thirteenrd"; you're just used to it.

Is this st/nd/rd/th business a unique feature of English? (I know in German, for example, numbers used as adjectives take an adjective ending based on the gender and case of the noun they are modifying. It's not based on rank at all. And in French, you just add "ième" regardless, unless it's the first.)

  • 3
    Why? Hysterical raisins. I think you want an etymology tag...
    – Drew
    Commented Feb 23, 2021 at 23:32
  • They should go "oneth", "twoth", "threeth", "fourth", "fiveth"!! They only got "fourth" right. :-(
    – Hot Licks
    Commented Feb 24, 2021 at 1:42

1 Answer 1


It does not depend on whether the ones digit is a 1, 2, or 3; it depends on whether the number is pronounced with a "one", "two", or "three" at the end. Eleven, twelve, and thirteen do not meet the pronunciation criterion and thus get lumped in with the rest of the "regular" numbers.

(Why they're called eleven, twelve, and thirteen instead of oneteen, twoteen, and threeteen is a completely different question....)

  • No answer to the old post to which you link mentions the possible contribution of the practice of counting in "scores" or batches of twenty. Both English and French have this, French particularly since the French numbers between eighty an ninetynine are based on "quatrevignt" which can be translated not only as "fourtwenty" but also, more familiarly, as "fourscore". Traditional sheep counting systems in England were based on scores including the notion of a notch being carved in a stick for every twenty counted, I believe that this might even be the origin of "score" for twenty.
    – BoldBen
    Commented Feb 24, 2021 at 9:12

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