Meaning of “their” - Learner’s Dictionary

their

determiner uk us /ðeər/
OF A GROUP

A1 belonging to or relating to a group of people, animals, or things that have already been talked about:

It was their problem, not mine.
HIS/HER

B1 used to refer to what belongs to or relates to a person when you want to avoid saying 'his' or 'her' or when you do not know if the person is male or female:

Did this person give their name?

(Definition of “their” from the Cambridge Learner’s Dictionary © Cambridge University Press)