(n.) The mark ['] used to denote that a word is contracted (as in ne'er for never, can't for can not), and as a 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.
APOSTROPHE
Meaning of APOSTROPHE in English
Webster's English dictionary. Английский словарь Webster. 2012