The difficulty over the apostrophe starts when we move on to plural nouns. The problem arises from thinking that the apostrophe has something to do with making words plural. It does not. To repeat the point we made earlier: adding’s has nothing to do with making words plural.
We usually make nouns plural by adding s; so, for example, cat becomes cats; student becomes students. There are, though, some words which make their plurals differently: the plural of child is children; leaf becomes leaves; kiss becomes kisses; mouse becomes mice. Most ... Read more...