In rhetoric and literary studies, the word apostrophe is a technical term. It is the name of a figure of speech. Apostrophe is what happens when a writer (or speaker) uses words to speak directly to a person who is not actually present: as if calling up a spirit in the air and talking to it. The narrator (the eponymous heroine) of Charlotte Bronte's novel Jane Eyre ends by saying "Reader, I ..." and then tells us what happened. (AWE will not spoil the story for those who want to read it: those who have read it will remember.) To address her audience directly like this, in the singular, is an example of apostrophe.
In older texts, and those written in the older tradition, an apostrophe is often signalled by the use of thou. Wordsworth's famous lines in To the Cuckoo:
- O Cuckoo! Shall I call thee bird
- Or but a wandering voice?
- Where Thou, great ANNA, whom three realms obey...
- (Pedants will insist that the name of the rhetorical device should be pronounced distinctly from that of the the punctuation mark the apostrophe. The rhetorical term was adopted into English from the French, where it has three syllables, 'a-po-stroff' (IPA: /a pɒ strɒf/). But the French word too is derived from Greek στροφὴ ('strophe') 'a turning', through άπὀστροφος, an adjective meaning 'of turning away', or 'of elision', so all but pedants may ignore this.)