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.
The words manner and manor are homophones: they sound alike but have different meanings. The noun manner means a customary or characteristic way of doing something or behaving. In the plural, manners (whether good or bad) usually refers to a person's habitual way of behaving in the company of others. The noun manor refers to a mansion or a large house with land.