A more thorough explanation:

Definition: A sergeant is a noncommissioned officer in the armed forces who ranks above a corporal. They are also an officer in the police force who ranks below a captain or lieutenant. In history, a sergeant could also be:

1. A person who held lands by tenure of military service but was not a knight.
2. A municipal officer who performed duties for the Crown.
3. A bailiff.
4. A sergeant-at-arms.

Examples:

• John was promoted to sergeant after serving as a corporal for two years in the army.
• The police sergeant was in charge of the investigation into the robbery.
• In medieval times, a sergeant was a person who held lands by tenure of military service but was not a knight.

The first two examples illustrate the modern usage of the term "sergeant" in the armed forces and police force. The third example shows how the term was used historically to refer to a person who held lands by tenure of military service but was not a knight. This definition is no longer in use today.