What is an apostrophe?

An apostrophe is a punctuation mark used to indicate possession or to show the omission of letters or numbers in a word or phrase.

For possession, it is used after the noun (or sometimes pronoun) and before the "s" to show that something belongs to that person or thing. For example: "Sarah's car" or "the dog's toy".

When showing omission, it is used to replace one or more letters in a word, often in contractions. For example: "can't" (short for "cannot"), "I'm" (short for "I am"), or "shouldn't" (short for "should not").

It is important to note that an apostrophe should not be used to make a word plural. This is a common mistake and can be seen as grammatically incorrect.