What does apostrophe mean?
The definition of apostrophe
A*pos”tro*phe, n.
Etym: [(1) L., fr. Gr. apostrophus apostrophe, the turning away or omitting of a letter, Gr.

1 (Rhet.)
A figure of speech by which the orator or writer suddenly breaks off from the previous method of his discourse, and addresses, in the second person, some person or thing, absent or present; as, Milton’s apostrophe to Light at the beginning of the third book of “Paradise Lost.”
2 (Gram.)
The contraction of a word by the omission of a letter or letters, which omission is marked by the character [‘] placed where the letter or letters would have been; as, call’d for called.
3 The mark [‘] used to denote that a word is contracted (as in ne’er for never, can’t for can not), and as sign of the possessive, singular and plural; as, a boy’s hat, boys’ hats. In the latter use it originally marked the omission of the letter e.

Note: The apostrophe is used to mark the plural of figures and letters; as, two 10’s and three a’s. It is also employed to mark the close of a quotation.