An example of a sergeant is an Army officer who is senior to a corporal.
An example of a sergeant is a police officer who is junior to a captain.
Origin of sergeant
- Middle English sergeaunte a common soldier from Old French sergent from Medieval Latin serviēns servient- servant, soldier from Late Latin public official from Latin present participle of servīre to serve from servus slave
From American Heritage Dictionary of the English Language, 5th Edition