You should use an apostrophe to form the possessive case of a
noun or to show that you have left out letters in a contraction.
Note that you should not generally use contractions in formal,
academic writing. - The convertible's engine has finally died.
(The noun "convertible's" is in the possessive case) - I haven't
seen my roommate for two weeks. (The verb "haven't" is a
contraction of "have not") To form the possessive of a plural
noun ending in "s," simply place an apostrophe after the "s." -
He has his three sons' futures in mind. - In many suburbs, the
houses' designs are too much alike. Possessive pronouns -- for
example, "hers," "yours," and "theirs" -- do not take
apostrophes. This is the case for the possessive pronoun "its"
as well: when you write "it's" with an apostrophe, you are
writing a contraction for "it is." - The spaceship landed hard,
damaging its radar receiver. ("its" is the possessive pronoun) -
It's your mother on the phone. ("it's" is the contraction of "it
is") Written by Frances Pec