HSK 6
备用
bèiyòng动
reserve; spare; alternate; backup
包里还有一把备用钥匙。
Bāo lǐ hái yǒu yì bǎ bèi yòng yào shi.
There is also a spare key in the bag.
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Other HSK words sharing a character
Also free:
New in the HSK 3.0 word list at level 6.