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You do not need an apostrophe here. Theirs is already in the right form. Their by itself is plural, because you are saying their book, meaning more than one person who owns the book. You only need to add 's, when you are dealing with singular words. The building's tenth floor was on fire.
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The first three sentences of the above answer are correct; the latter two are incorrect and irrelevant...
"They" (as with "him", "her", and "it") is a pronoun, therefore it does not require an apostrophe to be made possessive (i.e., the possessive forms of the above are "theirs", "his", "hers", and "its").
For more detail on apostrophes as indicators of possession:
If it is singular, add "'s" (apostrophe s).
If it is plural and ends in "s", add "s'" (s apostrophe). This is most plurals.
If it is plural but does not end in "s" (ex. "children", "men"), add "'s" (apostrophe s).
If it is plural but does not end in "s", but is the same as the singular (ex. "elk" is plural of "elk", therefore "elk's" is singular and "elks'" is plural).
What else can I help you with?
Do you use an apostrophe with theirs?
No! * The prize is theirs. * Theirs is the glory,
Should there be an apostrophe in the word theirs?
No. Ours is a possessive pronoun. It requires no punctuation to show possession.
Is the apostrophe for fishermans' in the right place?
Is the apostrophe for fishermans' in the right place? If you are talking about a fisherman and his boat, it would be "the fisherman's boat is ..."
Which part of speech never gets an apostrophe to indicate possession?
Possessive pronouns do not have apostrophes. Examples: his, hers, theirs, yours, and ours.
Why don't theirs and hers have apostrophes?
In the possessive pronouns "theirs" and "hers," the "s" already indicates possession, so apostrophes are not needed. Including an apostrophe, such as in "theirs" or "her's," would be grammatically incorrect.
Do you use an apostrophe with theirs?
No! * The prize is theirs. * Theirs is the glory,
Should there be an apostrophe in the word theirs?
No. Ours is a possessive pronoun. It requires no punctuation to show possession.
Is the apostrophe for fishermans' in the right place?
Is the apostrophe for fishermans' in the right place? If you are talking about a fisherman and his boat, it would be "the fisherman's boat is ..."
Is the apostrophe in the right place the man's uniform?
Yep :)
Which part of speech never gets an apostrophe to indicate possession?
Possessive pronouns do not have apostrophes. Examples: his, hers, theirs, yours, and ours.
Is the apostrophe in the right place for their book's?
Actually, when using a plural noun such as "books", there is no apostrophe. I hope that answers your question.
Is the apostorphe in the right place in the man's uniform?
Yes, but you mis-spelt apostrophe.
Is there an apostrophe in members' summer ball?
Yes, and you've put it in the right place
If written The man's uniform - is the apostrophe in the right place?
If you are intending to refer to a uniform that belongs to a man, then the correct placement of the apostrophe is as you have it. This is called the possessive form.
What is the purpose of an apostrophe in a contraction?
The apostrophe in a contraction holds the place of a letter or group of letters. Example: Don't = Do not (the apostrophe holds the place of the 'o') They've = They have (the apostrophe holds the place of the 'ha')
Write the possessive form of it?
The possessive form of it is "its." Notice that there is no apostrophe. "It's" is a contraction for "it is" or "it has." "Its" without an apostrophe is the possessive form of it. The same holds true for his, hers, ours, and theirs -- none of these have apostrophes.
Do you put an apostrophe for ownership on its?
Possessive pronouns do not take apostrophes. Some examples of possessive pronouns are: its, hers, his, theirs.
