Learning English

Meaning and use

We use the zero conditional to talk about things which always happen if a particular action takes place. These can be scientific facts, or things we believe are always true.

When you take exercise, your heart beats faster.
If I drink milk, I get stomach ache.

We can use if or when with the same meaning:

If you take exercise, your heart beats faster.
When I drink milk, I get stomach ache.

We use the first conditional to talk about things which might happen if an action takes place. We use if for things which are likely to happen and when for things which are certain to happen.

If I see Freddy later, I’ll give him the book. (I’m not certain I’ll see him.)
When I see Freddy later, I’ll give him the book. (I’m certain I’ll see him.)

If we go to the beach, I’ll take my swimsuit. (It isn’t certain we’ll go to the beach.)
When we go to the beach, I’ll take my swimsuit. (It is certain we’ll go to the beach.)

Form

Conditional sentences have two parts: the if/when part and the result (main) part. The two parts can come in any order. When we write, we don’t use a comma when the main part comes first.

I get stomach ache when I drink milk.
I’ll take my swimsuit if we go to the beach.

Zero conditional:

The zero conditional uses if/when + present simple, and present simple:

If/When you heat water to 100°C, it boils.

Positive

When she eats too much cake, she feels bad.
We always have a good time if we go dancing.

Negative

I feel upset when he doesn’t answer my calls.
If you mix white and yellow, you don’t get orange.

Question

What comes out of a volcano when it erupts?
Do eyelashes grow again if you cut them off? Yes, they do. / No, they don’t.

First conditional:

The first conditional uses if/when + present simple, and will + infinitive (without ‘to’):

If/When we go to Paris, we'll visit the Eiffel Tower.

Positive

I’ll do the cooking this evening if it’s OK with you.
When they finish work, they’ll go home.

Negative

I won’t wait for you, if you’re late again.
When we go camping, we won’t take our laptops.

Question

Where will he live when he moves to the city? 
If I don’t see you later, will you call me? Yes, I will. / No, I won’t.

Take note: the zero conditional and time

We use the zero conditional to talk about things which are always true. We use the present tense, but we are talking about all time (past, present and future).

If you multiply 10 by 10, it makes 100.
Plants grow when they get water and sunshine.

Take note: the first conditional and modals

We can use modals instead of will in first conditional sentences. For example, we can use may, might, can or should. We use may or might in the main part to show we are less certain than will, should to give advice, and could for possibility.

We might go shopping later if we have enough time.
If you don’t feel well, you should stay at home tonight.
When we finish our homework, we could watch TV.

Spoken English

In the first conditional, we often use the short form ’ll in the main part instead of will. This short form can sometimes be difficult to hear, but it’s important to include the ’ll sound. If you use the present tense in both parts, your sentence will sound like a zero conditional – and it won’t be grammatically correct!

If we miss our flight, we’ll take the next one. (Not: … we take the next one.)
They’ll meet us at the airport if we arrive late. (Not: They meet us at the airport …)