备用 bèiyòng reserve
reserve; spare; alternate; backup
How to remember 备用: 备 prepare + 用 to use (Kangxi radical 101) = reserve.
Characters
How it is used
- Spare / backup, kept in reserve: 备用钥匙 (bèiyòng yàoshi) spare key, 备用电源 (bèiyòng diànyuán) backup power.
- Attributive before a noun; signals 'held ready in case the main one fails.'
- Contrast 备份 (bèifèn), specifically a data backup/copy; 备用 is any standby item.