CONDITIONALS: ZERO & FIRST

IF (there is a chance)

WHEN (we are certain)

Examples:

IF I dance, I feel happy.

WHEN I dance, I feel happy.

When the sun sets, it gets dark.

If you leave milk out, it spoils.

If the power goes out, we can't watch TV.

A) In winter it's cold

B) If it's cold, light the fire.

Sentence A is a fact but it doesn't have two clauses. So, it is just a present simple sentence.

Sentence B has two clauses: a condition and the result. So, it is a ZERO conditional sentence that can be used to give instructions because of the imperative form of light

RULES: Children can swim, if an adult is with them.

HABITS: If it's hot, I go to the beach.

We're stating a fact or a truth in the main clause but it's only possible on the condition that the if clause occurs

If you don't eat now, you'll be hungry later.

If she doesn't call, I'll be annoyed.

If this thing happens then this will likely happen. It will probably happen. We can't be absolutely sure.

‘WHEN' tells us that the action in the if clause is going to happen and the result in the main clause is the most likely outcome.

eg: When the sun sets, it will get cold.