‘31th’ or ‘31st’ - Which is Correct?

By Shanea Patterson, updated on November 10, 2022

Should you write ‘31th’ or ‘31st'? Ordinal numbers can be difficult to remember how to use if English isn’t your first language because they change with different numbers. But we’ll cover ordinal numbers, plus how to use this one correctly in a sentence.

The short answer is:

  • ‘31st’ is the correct one.
  • It’s never correct to say ‘31th.’

How to Write Ordinal Numbers

Writing ordinal numbers can be tricky for someone learning English for the first time. But with a bit of practice, you’ll be well-versed in how to write ordinal numbers, no matter how high you’re trying to count.

Understanding Ordinal Numbers

 An ordinal number is “a number designating the place (such as first, second, or third) occupied by an item in an ordered sequence” and “a number assigned to an ordered set that designates both order of its elements and its cardinal number,” according to Merriam Webster.

Here’s how ordinal numbers would be written in word form:

  • First
  • Second
  • Third
  • Fourth
  • Fifth
  • Sixth
  • Seventh
  • Eighth
  • Ninth
  • Tenth

In numerical form, they’d be written like this:

  • 1st
  • 2nd
  • 3rd
  • 4th
  • 5th
  • 6th
  • 7th
  • 8th
  • 9th
  • 10th

The key is to remember that ordinal numbers generally repeat after 10 (with a few exceptions). For example, 11 would be eleventh (not like first).

  • 11th
  • 12th
  • 13th
  • 14th
  • 15th
  • 16th
  • 17th
  • 18th
  • 19th
  • 20th

But after this, we go back to using “first” just like we did with number one in the beginning of our count.

It would look like this:

  • 21st
  • 22nd
  • 23rd
  • 24th
  • 25th
  • 26th
  • 27th
  • 28th
  • 29th
  • 30th

This follows the first set of cardinal numbers we started with (first, second, third, etc.). From there, you’d simply follow this all the way up to 100. It’s odd that the numbers 11 through 20 follow a different set of rules than the rest of the numbers, but that’s just how it is.

31th or 31st? Which Spelling is Correct? 

As you learned above, it’s only correct to say ‘31st’ and not ‘31th.’

What is the Difference Between 31th and 31st?

The difference between the two is that the former is ungrammatical and incorrect, and the latter is the correct way to write the ordinal version of the number. 

How to Use ‘31st in a Sentence’ Correctly

Now that you’ve learned how to write ordinal numbers and you know what order they follow, you can write your own ordinal numbers. Use the following examples as a guide.

Here’s how you’d use ‘31st’ in a sentence correctly:

  • I’m taking tons of photos for my 31st birthday this year.
  • Halloween is on the 31st of October every year.
  • I want to be the 31st caller so I can win the prize.
  • Sorry to bother you, but is this the 31st floor?

Concluding Thoughts on ‘31th’ and ‘31st’

Now that you know the correct way to use ordinal numbers, you can use them correctly in your writing and in everyday life.

If you ever get stuck, just pop back on over and browse our library of articles on confusing words.

We can also teach you how to write better and understand common English idioms.

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Written By:
Shanea Patterson
Shanea Patterson is a writer based in New York and loves writing for brands big and small. She has a master's degree in professional writing from New York University and a bachelor's degree in English from Mercy College.

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