Both countries believe the territory is rightfully theirs.两国都认为这理应是他们的领土。

Your priorities may not be the same as theirs.你的重点可能和他们的不一样。

Whose car is that?—It's theirs.那是谁的车？——他们的。

Theirs had been a very happy marriage.那时他们的婚姻很美满。

a friend of theirs他们的一位朋友

I don't know whose laptop it is. Somebody must have left theirs.我不知道这是谁的笔记本电脑, 准是有人落下的。