a soldier of middle rank

Sergeant Lewis/Tom Lewis 刘易斯军士／汤姆·刘易斯军士

[ as form of address ] Dismiss the men, Sergeant. 军士，解散部下吧。

in the UK and some other countries, a police officer whose rank is above constable and below inspector, or, in the US, a police officer whose rank is below a captain

Sergeant Bates/Bill Bates 盖茨警佐／比尔·盖茨警佐

[ as form of address ] Thank you, Sergeant. 谢谢你，警佐。