Apostrophe is a figure of speech in which a poem speaks directly to someone or something that is absent, dead, imaginary, or unable to reply. The speaker may address a person, a place, an object, or an abstract idea as if it could hear. This should not be confused with the punctuation mark or possessive apostrophe.
An example is Wordsworth's sonnet Milton which begins: 'Milton! thou shouldst be living at this hour'. NB not to be confused with an apostrophe indicating missing letters or the possessive case. Other examples of apostrophe include A Supermarket in California by Allen Ginsberg (addressed to Walt Whitman) and my own poem Invocation.
Example
O winter sky, with your hard blue face,
why do you watch me from such a great height?
I ask the bare tree for an answer,
and its black branches only reach.
[n] the mark (') used to indicate the omission of one or more letters from a printed word
[n] address to an absent or imaginary person