sir

Used as an honorific before the given name or the full name of baronets and knights.

Used as a form of polite address for a man.

Used as a salutation in a letter.

To address as “sir.”

To use the word sir.

A master; lord; sovereign.

A person of rank or importance; a personage; a gentleman.

Master; mister: a respectful and formal title of address, used formerly to men of superior rank, position, or age, and now to men of equal rank, or without regard to rank, as a mere term of address, without etymological significance.

Specifically— A title of honor prefixed to the Christian names of knights and baronets, and formerly applied also to those of higher rank, as the king; it was also prefixed occasionally to the title of rank itself: as, Sir King; Sir Knight; Sir Herald.

(b ) Formerly, a title of a bachelor of arts; hence, a title given to a clergyman; also, a clergyman.