Theirs vs Their’s

Theirs vs their's
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Mixed up English

What’s the difference between theirs and their’s?


Theirs is the third person plural possessive pronoun – it replaces the possessive adjective "their" + a noun.

He found a book – is it theirs?

Is this yours or theirs?

I can’t find my keys, but theirs are on the table.

Theirs is a better idea.

Theirs is over here.


Though you may see their’s written even by native speakers, it is incorrect. Theirs should never have an apostrophe.

The Bottom Line

The idea that theirs needs an apostrophe comes out of the fact that on virtually every other word, ‘s indicates possession, so English speakers sometimes think theirs should be spelled their’s. However, this is always incorrect – theirs is the only correct spelling.

Related difficulties

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Theirs vs their's

8 Responses

  1. Shelly Kegan 26 April 2014 / 14:59

    This is not exactly true, the current spelling of theirs comes from middle english their’s.

  2. Mark 26 February 2015 / 09:34

    The comment still doesn’t answer WHY? If all other possessive words use an apostrophe then why is it wrong or incorrect to do add it on this single word? What is the rule? What is the reason?

  3. lkl 28 February 2015 / 07:12

    I can’t answer that. Sometimes grammar just is. Why do we say “I walk, you walk, we walk, they walk” but “he walks”? That’s just the way the grammar evolved. In the case of possessives, “their’s” simply is not a word. It’s wrong.

  4. duggan 15 March 2015 / 04:48

    Actually, I was always taught “theirs” and “their’s” are BOTH wrong.
    “Is this their book?” not “Is the book theirs/their’s?”

    as “their” in itself is possessive.

  5. lkl 15 March 2015 / 18:06

    No, “their” is a possessive adjective, while “theirs” is a possessive pronoun. You could make the argument for your example, but what about this one?

    “Whose house is this?”
    “It’s theirs.”

    It would sound silly to repeat house, as in “It’s their house.”

  6. Phillip McIntosh 16 March 2015 / 04:21

    Three different things: (1) possessive nouns as described above. (eg. Peter’s car) (2) possessive adjectives: my, your, his, her, our, its (this is “its” nest) their (eg. It is their car). (3) possessive pronouns: mine, yours, ours, his, hers, theirs. (eg. The blue car is theirs). The words in groups 2 and 3 never change form. Supposedly “its” fits into group 3 as well but personally I think it is obsolete. (eg. That nest is its? No way would you say that!)

  7. mofo80503 23 March 2017 / 19:43

    Thank you for helping me on this. I’m sure I’ll be back often.

    I thought it was ‘theirs’ but then I get to overthinking…

  8. lkl 24 March 2017 / 16:25

    Happy to help! 🙂

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