◎What you'll master
- Use the zero conditional (if/when + present, present) for general truths and facts.
- Use the first conditional (if + present, will/can/may + base) for real, possible futures.
- Use the second conditional (if + past, would/could/might + base) for unreal or unlikely situations.
- Punctuate correctly: a comma when the if-clause comes first, none when it comes second.
- Master the golden rule — never put will or would in the if-clause.
1What a conditional is
A conditional links a condition (the if-clause) to a result (the main clause). The tense you choose tells the listener how real or likely the situation is. In this lesson we cover the first three types: zero, first, and second.
Punctuation
When the if-clause comes first, put a comma before the main clause. When the main clause comes first, use no comma.
2The three types at a glance
| Type | If-clause | Main clause | Use |
|---|---|---|---|
| Zero | if/when + present | present | general truths & facts — always true |
| First | if + present | will/can/may + base | real, possible future |
| Second | if + past simple | would/could/might + base | unreal or unlikely present/future |
Notice: the tense in the if-clause is one step "further back" than the meaning — the past simple in a second conditional does not refer to past time; it signals unreal.
3Zero conditional — general truths
Use if or when + present simple in both clauses for things that are always true: facts, science, habits, and instructions. Here if and when mean almost the same thing.
4First conditional — real, possible future
For a real possibility in the future, use if + present simple in the condition and will / can / may / might + base verb in the result. The present tense in the if-clause already points to the future — that is why will is not allowed there.
"unless" = "if not"
Unless introduces the negative condition, so it already carries a "not" — don't add a second one.
5Second conditional — unreal or unlikely
For situations that are imaginary, unlikely, or contrary to fact now, use if + past simple in the condition and would / could / might + base verb in the result.
6'when' vs 'if', and the golden rule
Use when for something you expect to happen; use if for something that may or may not happen. "When I see her, I'll tell her" = I will see her. "If I see her, I'll tell her" = maybe I will, maybe not.
If you heat ice, it ______.
If it rains, we ______ in.
When water reaches 100°C, it ______.
If I ______ you, I'd apologise.
If he studied harder, he ______ pass the exam.
______ I see her, I'll tell her — I'm sure I'll meet her tomorrow.
If the government invested more in schools, results ______ across the whole country.
Send me the report tonight, and if I ______ time in the morning, I'll review it before the meeting.
✎Fix the Error
Each sentence has one mistake in the underlined word. Type the correction and check.
1.If it will rain, we'll stay in.
2.If I would have time, I would travel more.
3.If I was you, I'd apologise to her.
4.Unless you don't hurry, we'll miss the train.
5.When I will see her, I'll tell her the news.