The definition of an adjective is a part of speech that is used to describe a noun. Red, tall, better and fast are all examples of adjectives.
In modern parlance, a gentleman (from gentle + man, translating the Old French gentilz hom) is any man of good, courteous conduct. A gentleman may also simply be a polite term for any man, as in indications of gender-separated facilities, or as a sign of the speaker's own courtesy when addressing others. The modern female equivalent is lady.
Monsieur (French pronunciation: ; pl. Messieurs; 1512, from Middle French mon sieur, literally my lord) is an honorific title that used to refer to or address the eldest living brother of the king in the French royal court.