Apostrophes - part 1
An apostrophe can be used to replace a letter (or letters). For example:
isn't (from is not)
don't (from do not)
can't (from cannot)
When this happens, a new word (called a contraction) is formed.
Apostrophes Replace Missing Letters
An apostrophe can be used to show that a letter (or letters) is (are) missing from a word. Using an apostrophe to replace a missing letter is not common in formal writing, where you'd expect all words to be written in full. (Using an apostrophe to replace a letter is extremely common, but it is generally reserved for informal writing. It is used to reflect how people speak.) Examples:
The weather's bad.
(Written in full: The weather is bad.) (In this example, the apostrophe replaces the letter i, and the two words are joined to make one. The new word "weather's" is a contraction.)
Don't think about it.
(In full: Do not think about it) In this example, the apostrophe replaces the letter o, and the two words are joined to make a contraction.)
Apostrophe error found in a Christmas cracker
Alan can't deliver on Tuesdays.
(In full: cannot)
If you don't fail now and again, it's a sign you're playing it safe. (Woody Allen)
(In full: do not / it is / you are)
Don't look now, but there's one too many in this room, and I think it's you. (Groucho Marx)
(In full: do not / there is / it is)
Blood's not thicker than money. (Groucho Marx)
(In full: blood is)
Sally isn't able to complete her work.
(In full: is not)
Only Use Apostrophes to Replace Letters in Standard Contractions
When an apostrophe replaces a letter, a new word is formed (most often, but not always, using the remaining letters of the original words). The new word is called a contraction. You cannot invent your own contractions. Here is a list of common contractions in English:
aren't..........are not
can't..........cannot
couldn't..........could not
didn't..........did not
doesn't..........does not
don't..........do not
hadn't..........had not
hasn't..........has not
haven't..........have not
he'd..........he had, he would
he'll..........he will, he shall
he's..........he is, he has
I'd..........I had, I would
I'll..........I will, I shall
I'm..........I am
I've..........I have
isn't..........is not
it's..........it is, it has
let's..........let us
mustn't..........must not
shan't..........shall not
she'd..........she had, she would
she'll..........she will, she shall
she's..........she is, she has
shouldn't..........should not
that's..........that is, that has
there's..........there is, there has
they'd..........they had, they would
they'll..........they will, they shall
they're..........they are
they've..........they have
we'd..........we had, we would
we're..........we are
we've..........we have
weren't..........were not
what'll..........what will, what shall
what're..........what are
what's..........what is, what has
what've..........what have
where's..........where is, where has
who'd..........who had, who would
who'll..........who will, who shall
who're..........who are
who's..........who is, who has
who've..........who have
won't..........will not
wouldn't..........would not
you'd..........you had, you would
you'll..........you will, you shall
you're..........you are
you've..........you have