Many English learners get confused by 31th and 31st because both seem like they could be correct ordinal numbers. Since English has special spelling rules for dates and numbers, it is easy to make mistakes when writing them. You may have seen 31th in online posts, messages, or typing errors, but that does not make it correct.
Understanding the difference between 31th and 31st will help you write dates accurately in school, at work, and in everyday communication. In this guide, you’ll learn the correct form, why people confuse these words, and simple tricks to remember the right spelling forever.
Table of Contents
- Introduction
- Why “31th” and “31st” Are Confusing
- 31th vs 31st Explained Simply
- Understanding Homophones in English
- What Does “31th” Mean?
- What Does “31st” Mean?
- 31th vs 31st: Key Differences at a Glance
- How to Remember the Difference Between 31th and 31st
- Common Mistakes and Confusions
- Examples Section: Correct and Incorrect Usage
- Self Assessment: Test Your Knowledge
- Self Assessment Answers
- FAQs About “31th and 31st”
- Final Conclusion: Using “31th” and “31st” Correctly
Why “31th” and “31st” Are Confusing
Many learners wonder whether to write 31th or 31st because English ordinal numbers do not always follow the same pattern.
Similar Pronunciation
When spoken quickly, 31st may sound similar to what some learners imagine as 31th, especially if English is not their first language.
Similar Spelling
Both forms begin with 31, but they end differently:
- 31th ❌
- 31st ✅
The endings can be confusing because many numbers use -th, such as fourth, tenth, and hundredth.
Context Confusion
People commonly write ordinal numbers when mentioning:
- Dates
- Birthdays
- Anniversaries
- Events
- Rankings
Because several ordinal numbers end in -th, some learners mistakenly assume 31 should follow the same rule.
Common Learner Mistakes
Some frequent errors include:
- Writing 31th December
- Typing 31th birthday
- Using 31th place in competitions
In all these situations, 31st is the correct form.
31th vs 31st Explained Simply
The difference is very straightforward.
31st is the correct ordinal form of the number 31.
31th is an incorrect spelling and should never be used in standard English.
One-line distinction
31st means the ordinal form of thirty-one, while 31th is simply a spelling mistake.
Example Sentences
- The meeting will be held on 31st October.
- Her birthday falls on the 31st of July.
Understanding Homophones in English
Although 31th and 31st are not homophones, learners often confuse them because of English spelling patterns.
What Are Homophones?
Homophones are words that sound alike but have different meanings and spellings.
Example:
- Flower
- Flour
These two words sound the same but mean different things.
Why Homophones Cause Confusion
English learners often rely on pronunciation when spelling words. Since many ordinal numbers end with -th, learners may incorrectly extend that pattern to 31, producing 31th.
Example:
Correct:
- Today is the 31st of December.
Incorrect:
- Today is the 31th of December.
What Does “31th” Mean?
Definition and Core Meaning
31th has no meaning in standard English.
It is considered a spelling error.
Origin and Historical Use
There is no accepted historical use of 31th in modern English grammar.
It appears mainly because people mistakenly apply the -th ending to every ordinal number.
Modern Usage and Synonyms
There are no synonyms because the word is incorrect.
Key Points
- Not a valid English ordinal
- Considered a grammatical mistake
- Should always be replaced with 31st
- Avoid using it in academic or professional writing
Example Sentences
Incorrect:
- ✘ My appointment is on 31th May.
Incorrect:
- ✘ We arrived on the 31th.
What Does “31st” Mean?
Definition and Core Meaning
31st is the correct ordinal number for thirty-one.
It refers to the position of something in a sequence.
Origin and Historical Context
English ordinal numbers developed from Old English number forms.
Numbers ending in 1 generally take the suffix -st, except 11th.
Examples include:
- 1st
- 21st
- 31st
- 41st
- 51st
Modern Usage and Synonyms
You will commonly see 31st in:
- Calendar dates
- Rankings
- Anniversaries
- Birthdays
- Official documents
Synonyms
Depending on context:
- Thirty-first
- Number thirty-one (ordinal)
Example Sentences
- The project finishes on 31st August.
- She celebrated her 31st birthday.
- He ranked 31st in the race.
- The report was submitted on the 31st of January.
31th vs 31st: Key Differences at a Glance
| Word | Part of Speech | Meaning | Example Context |
|---|---|---|---|
| 31th | None (Incorrect Form) | Misspelling of 31st | ✘ 31th December |
| 31st | Ordinal Number | Thirty-first | ✔ 31st December |
How to Remember the Difference Between 31th and 31st
Here are some easy tricks.
Memory Trick 1
Numbers ending in 1 usually take -st.
Examples:
- 1st
- 21st
- 31st
- 41st
Memory Trick 2
Think about your birthday.
If your birthday is on the thirty-first day of the month, you would write:
31st, never 31th.
Memory Trick 3
Remember this simple rule:
If the number ends in 1, use st, unless the number is 11.
Memorable Example
✔ Halloween is on 31st October.
Whenever you think of Halloween, remember 31st, not 31th.
Common Mistakes and Confusions
Mistake 1
✘ Today is 31th July.
✔ Today is 31st July.
Explanation:
Thirty-one always becomes 31st.
Mistake 2
✘ My 31th birthday was amazing.
✔ My 31st birthday was amazing.
Explanation:
Birthdays use ordinal numbers.
Mistake 3
✘ She came 31th in the competition.
✔ She came 31st in the competition.
Explanation:
Rankings also require ordinal numbers.
Mistake 4
✘ The payment is due on 31th December.
✔ The payment is due on 31st December.
Explanation:
Dates always use the correct ordinal.
Examples Section: Correct and Incorrect Usage
Example 1
✔ Correct:
Our holiday begins on 31st December.
✘ Incorrect:
Our holiday begins on 31th December.
Example 2
✔ Correct:
She celebrated her 31st birthday.
✘ Incorrect:
She celebrated her 31th birthday.
Example 3
✔ Correct:
The event takes place on the 31st.
✘ Incorrect:
The event takes place on the 31th.
Example 4
✔ Correct:
He finished 31st in the marathon.
✘ Incorrect:
He finished 31th in the marathon.
Self Assessment: Test Your Knowledge
Fill in the blanks with 31st or 31th.
- My appointment is on ______ August.
- She celebrated her ______ birthday.
- Halloween is on ______ October.
- The report was submitted on the ______ of January.
Self Assessment Answers
- 31st
- 31st
- 31st
- 31st
FAQs
Is 31th correct in English?
No. 31th is incorrect. The proper ordinal form is 31st.
Why is it 31st instead of 31th?
Because ordinal numbers ending in 1 usually use the suffix -st, except 11th.
How do you write the date correctly?
Write:
- 31st December
- December 31st
Do not write 31th December.
Is 31th ever acceptable?
No. It is considered a spelling error in modern English.
Why do people write 31th?
Many learners mistakenly believe every ordinal number should end in -th.
How can I remember the correct spelling?
Remember this rule:
Numbers ending in 1 usually take -st (except 11).
Is “thirty-first” the same as 31st?
Yes.
Thirty-first is the word form, while 31st is the numerical abbreviation.
Final Conclusion: Using “31th” and “31st” Correctly
Understanding the difference between 31th and 31st is easier than it first appears. The key point to remember is that 31st is the only correct ordinal form of the number 31, while 31th is a common spelling mistake that should never be used in standard English. This rule applies whether you are writing dates, birthdays, anniversaries, rankings, or any other sequence involving the number thirty-one. Although many ordinal numbers end with -th, English follows specific patterns for numbers ending in 1, 2, and 3, which usually take the endings -st, -nd, and -rd respectively, with exceptions such as 11th, 12th, and 13th.
A simple memory trick is to think of familiar dates like 31st October or 31st December. Seeing these correct forms regularly will help reinforce the pattern until it becomes second nature. The more you read, write, and practice English, the easier these ordinal numbers will become. Whenever you are unsure, remember this simple rule: thirty-one always becomes 31st, never 31th. By mastering small grammar details like this, you improve your overall writing accuracy and communicate more confidently in both everyday and professional English. Keep practicing, and each new lesson will bring you one step closer to fluent and accurate English.
