Contractions are often used to speed up and shorten some common word combinations:

Contraction Meaning
I’m

I’ve

I’ll

I’d

I am

I have

I will

I had or I would

 you’re

you’ve

you’ll

you’d

 you are

you have

you will

you had or you would

 he’s

he’ll

he’d

 he is or he has

he will

he had or he would

 she’s

she’ll

she’d

 she is

she will

she had or she would

 it’s

it’d

 it is or it has

it had or it would

 we’re

we’ve

we’ll

we’d

 we are

we have

we will

we had or we would

 they’re

they’ve

they’ll

they’d

 they are

they have

they will

they had or they would

 there’s

there’ll

there’d

 there is

there will

there had or there would

aren’t

can’t

couldn’t

daren’t

didn’t

doesn’t

don’t

hadn’t

hasn’t

haven’t

isn’t

mightn’t

mustn’t

needn’t

oughtn’t

shan’t

shouldn’t

usedn’t

wasn’t

weren’t

won’t

wouldn’t

mayn’t (rare)

let’s

ain’t

are not

cannot

could not

dare not

did not

does not

do not

had not

has not

have not

is not

might not

must not

need not

ought not

shall not

should not

used not

was not

were not

will not

would not

may not

let us

am not, are not, is not, have not or has not

Source: Swan, Michael (1995), Practical English Usage, Oxford University Press, Oxford UK.