In typography, a punctuation mark (') used to denote possessive words and to stand in for omitted letters in contractions (as in don't).
The term apostrophe is also used in literature to refer to a rhetorical address to someone or something not actually present, found often in poetry, such as John Donne's "O Death, where is thy sting?" or John Milton's "Apostrophe to Light" (also called "On His Blindness").