Introduction
The zero conditional is a structure used for talking about general truths — things which always happen under certain conditions. This page will explain how the zero conditional is formed, and when to use it.
1. The structure of a zero conditional sentence
A zero conditional sentence consists of two clauses, an “if” clause and a main clause (In most zero conditional sentences you can use when or if and the meaning will stay the same.):
| “if” clause | main clause |
|---|---|
| If you heat water to 100 degrees, | it boils. |
If the “if” clause comes first, a comma is usually used. If the “if” clause comes second, there is no need for a comma:
| main clause | “if” clause |
|---|---|
| Water boils | if you heat it to 100 degrees, |
We use the same verb form in each part of a zero conditional: the simple present tense:
| “if” clause | if + subject + simple present verb |
|---|---|
| main clause | subject + simple present verb |
2. Using the zero conditional
The zero conditional is used to talk about things which are always true — such as scientific facts and general truths:
| Example | Explanation |
|---|---|
| If you cross an international date line, the time changes. | This always happens — every time you cross a date line. |
| If it rains, the grass gets wet. | This is basically always true — the rain makes the grass wet. |
| Wood doesn't burn if there is no air. | This is a scientific fact — wood needs air in order to burn. No air = no fire. |
When you are sure that you understand the lesson, you can continue with the exercises.