Use – to talk about general truths
E.g. If you have a brother or sister, you are not an only
Note: You are not an only child if you have a brother
Structure: If + present simple, present simple
Use – to talk about possible or likely situations now or in the
E.g. If it rains tomorrow, we’ll stay at home.
If + present tenses (simple, continuous and perfect) + will + b.i.
It is possible to use other modals instead of will:
If you finish the test early, you can go home.
If you work hard, you should pass the exam.
If I am tired, I may/ might decide not to go to the party.
Use – to talk about impossible or unlikely situations
now or in the future
E.g. If I found a wallet on the street, I would take it to the police
If I didn’t go to the party, I’d be upset.
If + past simple or continuous + would + b.i.
It is possible to use other modals instead of would:
I am not tired. If I went to bed now, I couldn’t sleep.
If I lived on my own, I might decide to get a dog.
In conditional sentences you can use WERE for all the subject
If I were rich, I would buy a big house.
Use – to talk about hypothetical situations in the past
E.g. I decided to stay at home last night. I would have gone out if I
hadn’t been so tired.
I wasn’t hungry. If I had been hungry, I would have eaten something.
If he had been looking where he was going, he wouldn’t have walked
into the wall.
If + past perfect simple or continuous + would have + p. p.
We can also use UNLESS in conditional sentences. UNLESS can replace IF ... NOT:
If we don’t score another goal, we will lose. (1st Cond.)
UNLESS we score another goal, we will lose.
I couldn’t watch the match if I didn’t have a TV. (2nd Cond.)
I couldn’t watch the match UNLESS I had a TV.
If she hadn’t been such a good player, she wouldn’t have won the game. (3rd Cond.)
UNLESS she had been such a good player, she wouldn’t have won the game.
Source: Laser Grammar Bank Intermediate. Macmillan. P. 23 -28.