A punctuation mark and sometimes a diacritic mark, in Latin fonts and languages. In English it has two main functions: it marks omissions, and it assists in marking the possessives of all nouns and many pronouns.
The apostrophe differs from the closing single quotation mark, often rendered identically but serving a different purpose. In limited casesit is allowed to assist in marking plurals, but most authorities now disapprove of such usage.
According to the OED, the word comes ultimately from Greek ἡ ἀπόστροφος [προσῳδία] (hē apóstrophos [prosōidía], the (accent of “turning away”, or elision), through Latin and French.