Theirs or Their's: What’s the Correct Usage?

If you’ve ever stopped mid-sentence and wondered whether to write “theirs” or “their’s”, you’re not alone. This is one of the most common grammar confusions in English, especially for beginners and even intermediate learners. Both words may look correct at first glance, but only one is actually grammatically right.

Many people search for “theirs or their’s” because English possessive forms can be tricky. Apostrophes are often used to show possession, so it feels natural to add one in their’s. However, English grammar has some special rules that make this case a bit different.

Understanding the correct usage is important for writing clearly and professionally. Whether you’re writing emails, essays, or social media posts, using the correct form builds credibility and avoids confusion.

Quick Answer

“Theirs” is correct. “Their’s” is incorrect.
“Theirs” is a possessive pronoun, and like other possessive pronouns (his, hers, ours), it does not need an apostrophe.

Meaning and Definition of Theirs or Their’s

1. Theirs (Correct)

Definition:
“Theirs” is a possessive pronoun used to show that something belongs to “them.”

Simple Explanation:
It replaces a noun to show ownership, so you don’t have to repeat the noun.

Examples:

This house is theirs.
The blue car is theirs, not ours.
That decision was completely theirs.

2. Their’s (Incorrect)

Definition:
“Their’s” is not a correct word in English.

Simple Explanation:
People mistakenly add an apostrophe because they think it shows possession. But possessive pronouns never use apostrophes.

Examples (Incorrect):

❌ This book is their’s.
❌ That idea was their’s.

Corrected Versions:

✅ This book is theirs.
✅ That idea was theirs.

Key Differences Between Theirs or Their’s

“Theirs” is correct, while “their’s” is incorrect
“Theirs” is a possessive pronoun
Possessive pronouns do not use apostrophes
“Their’s” is a common mistake caused by confusion with possessive nouns
“Theirs” replaces a noun, while “their” (without s) is used before a noun

Comparison Table

Word	Meaning	Usage	Example
Theirs	Belonging to them	Used without a noun	This bag is theirs.
Their’s	Incorrect form	Should not be used	❌ This bag is their’s.

Examples in Sentences

Using “Theirs” Correctly

The final decision was theirs.
That car outside is theirs.
The victory belongs to theirs team → ❌ (Incorrect structure)
✔ The victory is theirs.
These books are theirs, not mine.
The responsibility is completely theirs.

Comparing “Their” vs “Theirs”

This is their house. (used before a noun)
This house is theirs. (no noun after)

Common Mistakes

Mistake 1: Adding an Apostrophe

❌ This idea is their’s.
✅ This idea is theirs.

Why?
Apostrophes are not used in possessive pronouns.

Mistake 2: Confusing “Their” and “Theirs”

❌ This is theirs car.
✅ This is their car.
❌ This car is their.
✅ This car is theirs.

Mistake 3: Overusing Apostrophes

Many learners think:

Possession = apostrophe

But this is not always true.

Examples:

His (no apostrophe)
Hers (no apostrophe)
Theirs (no apostrophe)

Tips to Remember the Difference

Here are some simple tricks to remember:

1. Compare with “His” and “Hers”

We don’t write hi’s or her’s
So we also don’t write their’s

✔ If “his” doesn’t need an apostrophe, neither does “theirs”

2. No Apostrophe in Possessive Pronouns

Remember this rule:

👉 Possessive pronouns NEVER use apostrophes

Examples:

Mine
Yours
His
Hers
Ours
Theirs

3. Think: “Already Possessive”

“Theirs” is already showing ownership, so it doesn’t need extra punctuation.

4. Quick Test Trick

Replace “theirs” with “his”:

This book is theirs → This book is his ✅
This book is their’s → This book is hi’s ❌ (clearly wrong)

When to Use Each Word

Use “Theirs” When:

You are showing ownership
There is no noun after the word
You want to avoid repeating a noun

Examples:

That house is theirs.
The credit goes to theirs.
The fault is theirs, not ours.

Do NOT Use “Their’s”

There is no situation where “their’s” is correct.

Grammar Rules

Rule 1: Possessive Pronouns Don’t Use Apostrophes

Words like:

Mine
Yours
His
Hers
Ours
Theirs

👉 None of these use apostrophes.

Rule 2: Apostrophes Show Contractions or Nouns Possession

Apostrophes are used for:

Contractions
- It’s = it is
- Don’t = do not
Possessive Nouns
- John’s book
- The dog’s tail

But NOT for pronouns like “theirs”.

Rule 3: Difference Between “Their” and “Theirs”

Their → used before a noun
Example: Their house is big.
Theirs → replaces the noun
Example: That house is theirs.

Synonyms or Related Words

While “theirs” is specific, here are related possessive pronouns:

Mine
Yours
His
Hers
Ours

These follow the same rule no apostrophes.

Frequently Asked Questions (FAQs)

1. Is “their’s” ever correct?

No, “their’s” is always incorrect. The correct form is “theirs.”

2. Why doesn’t “theirs” have an apostrophe?

Because it is a possessive pronoun, and possessive pronouns do not use apostrophes.

3. What is the difference between “their” and “theirs”?

“Their” comes before a noun, while “theirs” replaces the noun.

4. Can I use “theirs” in formal writing?

Yes, “theirs” is completely correct and appropriate in both formal and informal writing.

5. How can I remember the correct form easily?

Just remember:
👉 If “his” doesn’t have an apostrophe, “theirs” shouldn’t either.

6. Is this sentence correct: “This is their book or theirs”?

It depends:

“This is their book” ✅
“This book is theirs” ✅
Don’t mix both in one phrase unnecessarily.

Conclusion

The confusion between theirs or their’s is very common, but the rule is actually simple. “Theirs” is the correct form, and “their’s” is always wrong. Since “theirs” is a possessive pronoun, it does not need an apostrophe.

By remembering that possessive pronouns never use apostrophes and comparing “theirs” with words like “his” and “hers,” you can easily avoid this mistake. Keep practicing with examples, and soon this confusion will disappear completely.