Summary: Prefixes are key morphemes in English vocabulary that begin words. The English prefix *non-*, which means "not," appears in hundreds of English vocabulary words, such as [*non*]sense, [*non*]fat, and [*non*]returnable. You can remember that the prefix *non-* means "not" via the word [*non*]poisonous, for a substance that is [*non*]poisonous is "not" poisonous.
