Apostrophes: The apostrophe mark (‘ ) has three main uses in English:
To make contractions
To make nouns and some pronouns possessive
To make letters of the alphabet plural
Contractions: An apostrophe shows where letters are missing in a contraction.
E.g.: isn’t is not
Possessive words show ownership. In the phrase Maria ‘s book, Maria’s is a possessive noun showing that Maria is the owner of the book. In English, we can show ownership with nouns in two ways. We can use an of the phrase and say the name of my friend, or we can use an apostrophe + s and say my friend’s name.
E.g.: the speed of the runner OR the runner’s speed
In general, we use an apostrophe or an apostrophe + s more often when the owner is a Jiving being, and we use the of phrase more often when the owner is a nonliving thing. We prefer, for example, to say the dog ‘s leg but the leg of the table. Sometimes you can write a possessive either way: The bank’s president or the president of the bank.
When the owner’s name is given, we don’t have a choice. We must use an apostrophe or apostrophe + s.
E.g.: Maria’s book NOT the book of Maria
Besides nouns, we also make indefinite pronouns possessive. Indefinite pronouns are the words someone, anyone, somebody, anybody, everyone, everybody, no one, nobody, and one.
E.g.: someone’s jacket
Plural of Letters of the Alphabet Use an apostrophe+ s to make letters of the alphabet plural.
E.g.: There are four s’s and four i’s in the word Mississippi .
E.g: The teacher gave ten A’s and two F’s last semester.