Sergeant and Second-class

Sergeant noun - Any of several noncommissioned officer ranks in the Army or Air Force or Marines ranking above a corporal.

Second-class and sergeant are semantically related. In some cases you can use "Second-class" instead a noun "Sergeant".

Second-class adjective - Of little or less value or merit.

Sergeant and second-class are semantically related. Sometimes you can use "Sergeant" instead a noun phrase "Second-class".