alternate

/ˈɔltərˌneɪt/

someone who takes the place of another person

Chinese meaning: 替代者；候补

The team selected an alternate in case the lead player got injured.

团队选了一名替补，以防主力队员受伤。

As an alternate, she had to be ready to step in at any moment.

作为候补，她必须随时准备接替。