Here are the rules that will apply: Rule one: If possessive noun is singular, then you need to add apostrophe plus “s”. Rule two: If possessive noun is not ending with the letter “s”, then you always need to add apostrophe plus “s”. Rule three: If possessive noun ends with the “s” and it is plural, what you only need to do is to add apostrophe.

Rules for the formation of the possessive -’s (apostrophe -s) and -s’ (-s apostrophe) are as follows: most singular nouns add an apostrophe + -s. a girl’s ring a cat’s face most plural nouns add an apostrophe after the plural form -s. the boys’ football five young girls’ faces