Apostrophe use.

Use one: to indicate contractions.

Place the apostrophe where there are missing letters.

For example:

He is ->he's   Missing i, therefore apostrophe is placed where it should be.

That seems simple enough.

Use two: to indicate possession.

A little more complex, but not that difficult.

If you were to write: the boy's house, boy needs an apostrophe because the house is his. The apostrophe indicates possession.

If you were to write: the boys house, it doesn't really make sense. Boys is now a plural and house is not a verb.

If there were two boys, you'd place the apostrophe after the s to indicate it is also a plural.

For example:

It was the boys' house. (ie/ Peter's and Paul's)

Singular noun possessive: apostrophe goes before the s.

Plural noun possessive: apostrophe goes after the s.

One exception is when dealing with collective nouns, such as children. While using the word children suggests more than one child, collective nouns are treated like singular nouns with the apostrophe before the s.

For example:

They went to the children's house.

Apostrophes are not used to indicate possession with pronouns. So, the dog licked its backside does not have an apostrophe, even though the backside is definitely his - and he can keep it.

Who's (who is) next? How about: their, there and they're?