I just realized that I’ve never needed to use 31th or 31st in my four years English study. So which one is correct, and what about other alternatives?

31th or 31st
101th or 101st
1001th or 1001st

Can I also use that way everywhere in the same way (for example, ordinal numbers in math)?

closed as general reference by Matt E. Эллен, JSBձոգչ, user2683, Mitch, kiamlaluno Nov 23 '11 at 2:37

This question is too basic; it can be definitively and permanently answered by a single link to a standard internet reference source designed specifically to find that type of information. If this question can be reworded to fit the rules in the help center, please edit the question.

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    Very interesting question, unfortunatelly I believe it is general reference, since single link to wikipedia answers it completely. Also, I would suggest you read it completely, from the way you asked the question I would not bet that you got the numbers up to 30th right. I might be wrong and that's what making this an interesting question (for me). – Unreason Nov 22 '11 at 19:43
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    @Unreason - Yes, i accept -it's general, but sometimes we really confused because of we're not native speaker and sometimes we need to be sure like this general questions. And look at below, even you guys are not exactly sure just about numbers.. but thanks :) – dino Nov 22 '11 at 20:08
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    This is very interesting question and you are completely right - the answer that you got from MetaEd is better than what is in general reference (it is shorter and does not go inventing rules where the matter can be explained easily). I hope it will not be closed. – Unreason Nov 22 '11 at 21:40
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    I disagree with those votes to close. The answer to OP's first question (which form is "correct"?) may well be trivial, but the second (what about other alternatives?) isn't - as shown by "one hundred and oneth" – FumbleFingers Nov 22 '11 at 23:15
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    @Mitch: If you want to be picky. But this question is closed as "general reference", not because it's a dup of the one you've only just linked to. You could have put that link in yourself earlier - given you've answered the other one I doubt you'd forgotten it. Anyway, I don't think the matter is fully covered there, even though I upvoted Neil and Peter's answers. I still think OP has asked three questions here, and the second should not be closed. – FumbleFingers Nov 23 '11 at 4:44

I think the 101st Airborne Division (U.S. Army infantry division trained for air assault) is a defining case for “standard” usage.

Having said that, in light of 6800 written instances of 101th I can’t say the alternative is “wrong”.

  • I'd like to see sentences and the context in which you found those written examples... Just because it's been written that way it doesn't mean it's correct. – FrustratedWithFormsDesigner Nov 22 '11 at 19:20
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    @onomatomaniak, one hundred oneth is exactly how I've (sometimes) heard it. Also, some of those occurrences might be computer-generated: it's much easier to tell a program to tack on a "-th" for all numbers above 3 than to mess around with exceptions or modulo-10 formulas. – Marthaª Nov 22 '11 at 19:41
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    If it had to be pronounced, I would imagine "one-oh-oneth". Although that still sounds awkward. – daxelrod Nov 22 '11 at 19:42
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    @Martha: Thanks for pointing out the relevance of "dumb computer code", but I doubt that applies to many of the written instances I linked to. – FumbleFingers Nov 22 '11 at 19:43
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    I agree with Onomatomaniak, it's too much of a stretch to pronounce 101th. Is it possible that the writer got carried away while writing and wrote 101th by mistake? I know it's sheer speculation, but it does sound unnatural. – Irene Nov 22 '11 at 19:46

The numerals with endings are merely abbreviations for the words written out as text. When in doubt, write the word out. Thirty-first becomes 31st, eleventh 11th, forty-second 42nd, fiftieth 50th, and so on.

  • Thank you +1, this is what I wanted to say. It is incredibly interesting that even wikipedia needs to define set of rules when rule is so simple. – Unreason Nov 22 '11 at 21:33

31st, etc. are the correct options. When you use ordinal numbers ending in 1, you use first. The only exception is eleventh, because although it ends in 1 its “name” doesn’t contain the word “one” like 21, 31, etc.

  • What about dates? 41st or 41th of February is correct? – dino Nov 22 '11 at 19:12
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    The only exception seems to be 11: Eleventh (11th) is correct, but Elevenst (11st) is not. – FrustratedWithFormsDesigner Nov 22 '11 at 19:13
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    @dinobeytar: If February had 41 days (it doesn't), then it would be 41st of February. – FrustratedWithFormsDesigner Nov 22 '11 at 19:14
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    Irene's explanation holds up for dates as well. There are also rules for numbers ending in 2 and 3 - use nd for 2 - 2nd, 748392nd; rd for 3 - 3rd, 38743rd. When dealing with teens these do not apply - 11th, 12th, 13th, 14th all the way to 19th are correct. – Mohandas Grande Nov 22 '11 at 19:16
  • @FrustratedWithFormsDesigner: You're right about 11th. I should have included it. Thanks for pointing it out and completed my answer. – Irene Nov 22 '11 at 19:16

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