spare

/spɛr/

an extra component of a machine or other apparatus

中文释义：备件；备用零件

Always keep a spare tire in your car in case of a puncture.

车上总要备一个备用轮胎，以防爆胎。

The mechanic ordered a spare part for the broken machine.

机械师为坏掉的机器订购了一个备件。