theirs
That or those belonging to them; the possessive case of they, used without a following noun.
Example
“This luggage is theirs. These passports are also theirs.”
Other meanings
Their house or home.
“Let's go over to theirs.”
Word history
From Middle English "theires".
Where this comes from
This definition is adapted from “theirs” on Wiktionary, by its contributors, published under CC BY-SA 4.0. This page is published under the same licence.