Conditional sentences

Zero conditional
We use the zero conditional to talk about things that are always true.

If you heat water, it boils.
When the sun goes down, it gets dark.
It lights up if you push that button.
The present simple is used in both clauses.

First conditional
We use the first conditional when we talk about real and possible situations.

I’ll go shopping on the way home if I have time.
If it’s a nice day tomorrow, we’ll go to the beach.
If Arsenal win, they’ll be top of the league.
In first conditional sentences, the structure is usually if + present simple and will + infinitive. It’s not important which clause comes first.

Second conditional
The second conditional is used to talk about ‘unreal’ or impossible things.

If I won a lot of money, I’d buy a big house in the country.
Where would you live if you could live anywhere in the world?
If you didn’t smoke so much, you’d feel a lot better.
The structure is usually if + past simple and would + infinitive. It’s not important which clause comes first.

Look at the difference between the first and second conditionals.

In January: If it snows tomorrow, I’ll go skiing. It might snow tomorrow.
In August: If it snowed tomorrow, I’d go skiing. It almost certainly won’t snow tomorrow.
NOTE: Although many conditional sentences use if + will/would, conditional sentences can also use other words instead of ‘if’ – e.g. ‘when’ ‘as soon as’ ‘in case’ Other modal verbs can be used instead of ‘will/would’ – e.g. ‘can/could’, ‘may’ ‘might’.