Apostrophe
Apostrof

1) With nouns (plural and singular) not ending in an s add 's.
the children's books, the people's parliament, a Mother's pride

2) With plural nouns ending in an s, add only the apostrophe.
the guards' duties, the Nuns' habits, the Joneses' house

3) With singular nouns ending in an s, you can add either 's or an apostrophe alone.
the witness's lie or the witness' lie (be consistent)
Exception: ancient or religious names.
Jesus' strength, Achilles' heel

4a) For common possession, only add 's to the last name.
Janet and Jane's house

4b) Where possession is not common, add to each.
Janet's and Jane's homes

Pronouns
With the exception of one's, pronouns (its, his, hers) do not require an apostrophe.
to indicate contractions

Where letters or numbers have been omitted.
the summer of '69, the house wasn't at its best, that isn't the right way, it's not bad