31st or 31th: Which One Is Correct and When to Use Each?📝

31st is correct, while 31th is incorrect in standard English.

Many people search for 31st or 31th because ordinal numbers in English follow special spelling rules that are not always obvious.

Writers often hesitate when adding endings like st, nd, rd, or th to numbers. This confusion happens in dates, invitations, emails, and formal writing where accuracy matters. A small mistake in number endings can make writing look unpolished.

This guide explains the rule clearly, shows why 31st is correct, and provides examples to help you remember easily. By the end, you will understand ordinal number endings and avoid this common mistake.

Table of Contents

31st or 31th: Quick Answer

✅ 31st is correct.
❌ 31th is incorrect.

Ordinal numbers follow patterns based on the last digit of the number.

Examples:

My birthday is on the 31st of July.
The event takes place on March 31st.

Quick rule: numbers ending in 1 usually take st (except 11).

31st or 31th in Dates: Correct Usage Examples

Many people search phrases like “December 31st or 31th,” “March 31st or 31th,” “October 31st or 31th,” and “January 31st or 31th.”

The rule does not change based on the month.

✅ Correct date formats:

December 31st
March 31st
October 31st
January 31st

❌ Incorrect forms:

December 31th
March 31th
October 31th
January 31th

👉 Key point:
No matter the month, 31st is always correct.

This also answers queries like:

“31th or 31st December” → 31st December ✅
“31th or 31st birthday” → 31st birthday ✅

The Origin of 31st or 31th

Ordinal numbers show position or order, such as first, second, or third. These forms come from Old English counting systems where special endings marked sequence rather than quantity.

Over time, English developed abbreviations:

first → 1st
second → 2nd
third → 3rd
fourth → 4th

The endings reflect pronunciation. Since “thirty-first” ends with “first,” the correct abbreviation becomes 31st. The form 31th does not match pronunciation or historical patterns, which is why it is incorrect.

British English vs American English Spelling

Both British and American English use the same ordinal number rules.

Comparison Table

Number	British English	American English	Example
31st	Correct	Correct	January 31st
31th	Incorrect	Incorrect	❌ January 31th

There is no regional difference. The rule is universal.

Which Form Should You Use?

Always use 31st in:

Dates
Lists
Rankings
Formal writing

Examples:

She finished in 31st place.
The deadline is the 31st of this month.

Avoid using 31th in any professional or standard context.

Common Mistakes with 31st or 31th

Mistake 1: Adding “th” to all numbers
Some learners think every ordinal uses “th.”

❌ 21th, 31th, 41th
✅ 21st, 31st, 41st

Mistake 2: Forgetting exceptions
Numbers ending in 11, 12, and 13 always use “th.”

11th, 12th, 13th

3: Mixing endings in dates
Stay consistent and follow ordinal rules.

31st or 31th: Common Search Questions Answered

Users often search variations like “is it 31st or 31th,” “is 31th correct,” “31rd or 31th,” “31 st or 31 th,” and “31th in words.”

Here are clear answers:

Is 31th correct?
❌ No, it is always incorrect.
Is it 31st or 31th?
31st ou 31th
✅ Always 31st
Can it be 31rd?
❌ No, “rd” is only for numbers ending in 3 (like 3rd, 23rd)
Should I write “31 st” or “31th”?
❌ Both are incorrect formats
✅ Correct: 31st (no space, no “th”)
How do you write 31th in words?
❌ 31th is wrong
✅ Correct form: “thirty-first”

Simple rule:
If the number ends in 1 (and not 11), always use st.

31st or 31th in Everyday Examples

Emails

The meeting is scheduled for the 31st.

News Writing

The contract ends on December 31st.

Social Media

Countdown to the 31st begins!

Formal Writing

Applications must be submitted by the 31st of May.

31st or 31th: Google Trends & Usage Data

Search data shows many users type “31th” because they assume all ordinal numbers use “th.” Learners and non-native writers often make this mistake.

Usage patterns show:

31st dominates in books, news, and professional writing.
31th appears mostly in search queries or informal mistakes.

This indicates users are looking for confirmation of the correct ordinal ending.

Comparison Table: Ordinal Number Endings

Last Digit	Correct Ending	Example
1	st	21st, 31st
2	nd	22nd
3	rd	23rd
4 :9 and 0	th	24th, 30th
Exceptions (11 :13)	th	11th, 12th, 13th

This simple chart helps you remember all ordinal endings quickly.

FAQs: 31st or 31th

1. Is 31th ever correct?
No. Standard English always uses 31st.

2. Why is it 31st instead of 31th?
Because the spoken form is “thirty-first,” which ends with “first.”

3. Do all numbers ending in 1 use “st”?
Yes, except 11, which becomes 11th.

4. Is the rule the same worldwide?
Yes. Both British and American English follow the same ordinal system.

5. Should I write “31st” or “31”?
Use 31st when indicating order or date context.

6. Can I write “the 31” instead of “31st”?
Sometimes, but ordinal form is clearer in formal writing.

7. Do pronunciation and spelling match?
Yes. The ending reflects how the ordinal number sounds.

Conclusion

The difference between 31st or 31th is simple once you understand ordinal number rules. English uses special endings st, nd, rd, and th to show position or order. Since the number 31 is pronounced “thirty-first,” the correct form is 31st.

The spelling 31th does not match pronunciation or grammar rules and should be avoided in professional writing.

This rule applies everywhere, as there is no regional variation. Learning the pattern for ordinal endings helps you avoid similar mistakes with other numbers.

By remembering that numbers ending in 1 usually take “st” (except 11), you can write dates and rankings confidently and correctly.

31st or 31th: Which One Is Correct and When to Use Each?📝

31st or 31th: Quick Answer

31st or 31th in Dates: Correct Usage Examples

The Origin of 31st or 31th