alternate

/ˈɔltərˌneɪt/

someone who takes the place of another person

中文释义：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。