An apostrophe is an exclamatory figure of speech.[1] It occurs when a speaker breaks off from addressing the audience (e.g., in a play) and directs speech to a third party such as an opposing litigant or some other individual, sometimes absent from the scene. Often the addressee is a personified abstract quality or inanimate object.[2][3] In dramatic works and poetry written in or translated into English, such a figure of speech is often introduced by the vocative exclamation, "O". Poets may apostrophize a beloved, the Muses, God or gods, love, time, or any other entity that can't respond in reality.
"O, pardon me, thou bleeding piece of earth, / That I am meek and gentle with these butchers! / Thou art the ruins of the noblest man / That ever lived in the tide of times." William Shakespeare, Julius Caesar, act 3, scene 1
"O happy dagger! This is thy sheath; there rest, and let me die." Romeo and Juliet, act 5, scene 3, 169–170.
"To what green altar, O mysterious priest, / Lead'st thou that heifer lowing at the skies, / And all her silken flanks with garlands drest?" John Keats, "Ode on a Grecian Urn"