Form
Formula: If / When + present simple, present simple
| If / When clause | Result clause |
|---|---|
| If you heat water to 100°C, | it boils. |
| If you don't water plants, | they die. |
| When I am tired, | I make mistakes. |
| If you press this button, | the machine starts. |
if vs when:
Both work in the zero conditional. If suggests a condition that may or may not happen. When suggests it always or regularly happens: "When I drink coffee, I feel better." (always true)
Clause order:
The if/when clause can come first or second. If it comes second, no comma is needed: "Water boils if you heat it to 100°C."
When to use the zero conditional
| Use | Example |
|---|---|
| Scientific facts / laws of nature | If you mix red and blue, you get purple. |
| General truths | If people don't sleep, they feel terrible. |
| Instructions / procedures | If the alarm sounds, everyone leaves the building. |
| Personal habits / routines | When I exercise, I feel much better. |
Three conditionals — quick overview
| Conditional | Form | Meaning |
|---|---|---|
| Zero | if + present, present | Always true — facts & general truths |
| First | if + present, will | Real / likely future possibility |
| Second | if + past, would | Hypothetical / unreal present situation |
Exercises
Complete the zero conditional. Choose the correct form.
1. If you ___ water below 0°C, it freezes.
2. Plants die if they ___ enough light.
3. If you press this button, the machine ___.
4. When I'm stressed, I usually ___ (eat) too much.