Answer:
Apostrophes are put in place of elided letters, e.g. don't, for, do, not, or fo'c's'l for forecastle. In the case of possessives, the rule is: 1) All singular nouns, regardless of spelling, take 's; 2) Plural nouns ending in s take the apostrophe alone, but plurals not ending in s take 's. For example, Russ's house, States' rights, women's sports.