Conditional ("if") sentences normally have two parts.
One part shows a result and the other shows a condition
on which the result depends. The condition is normally
preceded by if. In "He'd have gotten angry if he hadn't
gotten what he wanted," the result is "he'd have gotten
angry" and the condition (introduced by "if") is "he hadn't
gotten what he wanted."

There are two main types of conditional sentences: real
and unreal. Real conditional sentences refer to situations
that are either true or possible. Unreal conditionals refer
to situations that are untrue, impossible or hypothetical;
conditional sentences of this type are often described as
being contrary to fact.

Let's take another look at unreal conditionals.

There are several types of unreal conditional sentences.
They differ according to the time that they refer to, but
they are the same in one way: the situations that they
show are unreal, hypothetical, and contrary to fact.

The second type of unreal conditional is used for past
time. Normally, unreal conditional sentences that refer
to past time use this form:

 

If + subject + had + past participle +
other words, subject + would have ('ve) +
past participle + other words.

OR

Subject + would have ('ve) + past
participle + other words if + subject +
had + past participle + other words.

(This form is used for BE and other verbs.)

 

Examples:

If he had been here yesterday, he would've
helped you. / He would've helped you if he
had been here yesterday.

(He wasn't here yesterday, so he couldn't
help you.)

 

If I had had enough money, I would've
traveled around the world. / I would've
traveled around the world if I had had
enough money.

(I didn't have enough money, so I couldn't
travel around the world.)

 

If cars had cost less, I would've bought
a new one. / I would've bought a new car
if they had cost less.

(New cars cost too much for me, so
I couldn't buy one.)

 

Special Notes: