1.their是复数第三人称的所有格形式,是复数形容词性物主代词,在句中只可用作定语,其后常接复数名词。有时为了避免显示性别, their还可代替his, her用作anybody, anyone, everyone等词的物主代词,此时其后可接单数名词。有时their还可用作动名词的逻辑主语。
2.their还可与own连用构成强调。

Take a note of their names and addresses.把他们的姓名和地址记下来。
Has anyone bought their ticket?每个人都买到票了吗?
Their coming to help was a great encouragement to us.他们来支援对我们是很大的鼓舞。
The Pollaks had no children of their own.波拉克夫妇自己没有孩子。

［词源］＜古挪威语theirra(他〔她,它〕们的)