For singular nouns and plural nouns that do not end in -s (including words that end in -x or -z), add ‘s: New York’s fifth win in six games; the women’s bathroom; the Red Sox’s first championship; the Blitz’s biggest star

For singular nouns that end in -s, add only an apostrophe: LeBron James’ contract

For plural nouns that end in -s, add only an apostrophe: the Sixers’ home arena

For possessive pronouns, none take an apostrophe: mine, yours, ours, theirs, its, whose, etc.