Using Apostrophes to Create Contractions
Apostrophes are also used in contractions where the apostrophe takes the place of letters that are omitted when you join two words. Here are some examples:
you are = you’re
it is = it’s
did not = didn’t
You can also use an apostrophe to stand in for omitted numbers.
It’s important to note that contractions and using apostrophes to stand in for omitted numbers is generally considered too informal for formal, academic writing.
Some students wonder why they should bother learning these rules, then. The answer is that there are plenty of writing situations where contractions are appropriate. It’s just that contractions are too informal for most of the formal papers you write for college and should be avoided in those situations.