中士(zhōng shì) - sergeant in Mandarin

中士 (zhōng shì) is a rank, not a job description: the middle rung of the three non-commissioned grades that run 下士, 中士, 上士. English translates it as sergeant, and for most purposes that is close enough.

You will meet it in war films, news reports and any story with soldiers in it, usually as a title stuck straight in front of a surname: 王中士. The measure word is 位 or 名 when you are counting people politely.

The trap is 士 itself. It is not the everyday word for soldier, which is 士兵 or 军人, and it is not a general honorific either. Seeing 士 on the end of a two-character word almost always signals a formal rank or a professional class, so read 中士 as a slot in a hierarchy rather than as a bloke with a gun.