their

1. DET You use their to indicate that something belongs or relates to the group of people, animals, or things that you are talking about. 他們的; 她們的; 它們的

Janis and Kurt have announced their engagement. 賈尼斯和庫爾特已宣佈訂婚。

2. DET You use their instead of "his or her" to indicate that something belongs or relates to a person without saying whether that person is a man or a woman. Some people think this use is incorrect. 用於代替“他的”或 “她的”，不指明是男是女

Each student determines their own pace in the yoga class. 每個學生決定他們自己在這個瑜珈班的學習速度。