Apostrophe (etymology: a turning-away [from the main subject or addressee]) in literature is a rhetorical figure of direct address to (1): an absent or dead person; (2): an imaginary person such as a material object or an aspect of nature that is treated anthropomorphically: (3): a personified abstraction: For example:
(1) “Good night, sweet prince, / And flights of angels sing three to thy rest!” (Horatio in Hamlet V, ii, 348-49).
(2) “Thou still unravish’d bride of quietness, / Thou foster-child of silence and slow time” (etc. Keats’ “Ode to a Grecian Urn,” vv. 1-10).
(3) “They call you Lady Luck, / But there is room for doubt /. . . Luck, be a lady tonight” (Frank Loesser, “Luck,…
Porter, Laurence M.. "Apostrophe". The Literary Encyclopedia. First published 29 January 2012
[http://www.litencyc.com/php/stopics.php?rec=true&UID=69, accessed 21 February 2017.]