First-class and Sergeant

First-class adjective - Of the very best kind.

Sergeant and first-class are semantically related. In some cases you can use "Sergeant" instead a noun phrase "First-class".

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

First-class and sergeant are semantically related. Sometimes you can use "First-class" instead a noun "Sergeant".