The apostrophe ( ’ or ' ) is a punctuation mark, and sometimes a diacritical mark, in languages that use the Latin alphabet or certain other alphabets. In English, it serves three purposes:

• The marking of the omission of one or more letters (as in the contraction of do not to don't).
• The marking of possessive case (as in the eagle's feathers, or in one month's time).
• The marking by some as plural of written items that are not words established in English orthography (as in P's and Q's). (This is considered incorrect by others; see Use in forming certain plurals. The use of the apostrophe to form plurals of proper words, as in apple's, banana's, etc., is universally considered incorrect.)

Apostrophe (Greek ἀποστροφή, apostrophé, "turning away"; the final e being sounded) is an exclamatory figure of speech. 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. 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 Muse, God, love, time, or any other entity that can’t respond in reality.