Meaning of “their” - Learner’s Dictionary

their

determiner us uk /ðeər/
The children are grouped according to their ability.They've had to change their plans.The students were given a free hand as far as designing their product was concerned.Children need lots of encouragement from their parents.They finished their drinks and left the bar.
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)