Beginner · A2–B1
Conditionals: Zero Conditional
The zero conditional expresses general truths, facts, and things that always happen when a condition is met. It uses the present simple in both clauses.
Structure
If + present simple, present simple
Zero conditional
If you heat water to 100°C, it boils.
If it rains, the ground gets wet.
If you don't sleep enough, you feel tired.
When to use it
- Scientific facts and laws of nature: If you mix blue and yellow, you get green.
- General truths that always apply: If people don't eat, they get hungry.
- Instructions and cause-effect: If the alarm goes off, leave the building.
'When' vs. 'if'
In the zero conditional, when and if can often be used interchangeably — because the event is certain to happen.
When = if (zero conditional)
When/If you heat ice, it melts.
When/If she finishes work, she usually goes to the gym.
Clause order
The if-clause can come first or second. Use a comma when the if-clause comes first.
| Order | Comma? | Example |
|---|---|---|
| If-clause first | Yes | If you heat it, it melts. |
| Main clause first | No | It melts if you heat it. |
Tip: The zero conditional is for things that are always true. If the result is possible but not guaranteed, use the first conditional instead.