毫米 (háo mǐ) means “millimeter”. It is an HSK 6 Chinese word in the HSK 3.0 vocabulary.
Practice each character:
今天下了十毫米的雨。
Jīntiān xià le shí háomǐ de yǔ.
It rained ten millimeters today.
Updated: 2026-05-27