apos·tro·phe

/əˈpʰɑːstrəfi/ noun, pl -phes [count]

1 : the punctuation mark ’ used to show that letters or numbers are missing (as when “did” and “not” are combined into “didn't” or when the date 1776 is written as '76)

In the contraction “can't,” an apostrophe replaces two of the letters in the word “cannot.”

2 : the punctuation mark ’ used to show the possessive form of a noun (as in “Lee's book” or “the tree's leaves”)

3 : the punctuation mark ’ used to show the plural forms of letters or numbers (as in “dot your i's and cross your t's” or “in the 1960's”)