Conditionals and clauses
Zero and first conditional and time/condition clauses
A conditional sentence has two parts: an 'if-clause' (the condition) and a main clause (the result). We use the zero conditional to talk about general truths and scientific facts; both verbs are in the present simple, and 'if' often means 'when' (If you heat water to 100 degrees, it boils). We use the first conditional to talk about real or likely situations in the future; the if-clause uses the present simple and the main clause uses 'will' or 'won't' plus the base verb (If it rains, I will stay home). A very important rule is that we do not use 'will' in the if-clause or in a time clause, even though the meaning is future (NOT 'If it will rain'). The word 'unless' means 'if not', so 'I won't go unless you come' means 'I won't go if you don't come'. We follow the same rule with time clauses introduced by when, while, before, after, as soon as and until: the verb after these words stays in the present simple to talk about the future. For example: 'I will call you as soon as I arrive', not 'as soon as I will arrive'.
Key terms
| Type | If-clause | Main clause | Use |
|---|---|---|---|
| Zero | if + present simple | present simple | general truth or scientific fact |
| First | if + present simple | will/won't + base verb | real or likely future situation |
| Word | Meaning / use | Verb after it | Example |
|---|---|---|---|
| if | states a condition | present simple | If it rains, I will stay home. |
| unless | if not | present simple | I won't go out unless the rain stops. |
| when / while | time clause (future) | present simple | I will call you when I get there. |
| before / after | time clause (future) | present simple | Turn off the lights before you leave the room. |
| as soon as / until | time clause (future) | present simple | We will wait here until the rain stops. |
- 1Idea: State a fact that is always true: heating ice makes it melt.
- 2If-clause: Use 'if' (or 'when') + present simple: If you heat ice — not 'If you will heat'.
- 3Main clause: Use the present simple for the result too: it melts — not 'it will melt'.
- 4Full sentence: If you heat ice, it melts.
- 1Idea: Talk about a likely future situation: if it rains tomorrow, I stay at home.
- 2If-clause: Use 'if' + present simple, even for the future: If it rains tomorrow — not 'If it will rain'.
- 3Main clause: Use 'will' + base verb for the future result: I will stay at home.
- 4Full sentence: If it rains tomorrow, I will stay at home.
Never use 'will' in the if-clause. Say 'If it rains' and 'If she studies', not 'If it will rain' or 'If she will study' — even when the meaning is future.
Do not use 'will' after a time word (when, while, before, after, as soon as, until). Say 'I will call you when I get home', not 'when I will get home'.
'unless' already means 'if not', so do not add another negative. Write 'unless you return it', not 'unless you don't return it' — the second is a double negative.
In the zero conditional the result stays in the present simple (it melts), but in the first conditional the result uses 'will' + base verb (I will stay). Decide whether you are stating a general truth or predicting a real future before you choose the form.
Rules
- 1Zero conditional (general truths/facts): If/When + present simple, present simple — If you mix blue and yellow, you get green.
- 2First conditional (real/likely future): If + present simple, will/won't + base verb — If she studies, she will pass.
- 3Never use 'will' in the if-clause or a time clause: say 'If it rains' (NOT 'If it will rain').
- 4'unless' = 'if not': I won't go out unless the rain stops (= if the rain does not stop).
- 5After time words (when, while, before, after, as soon as, until) use the present simple for the future: I will text you when I get there (NOT 'when I will get there').
Practice
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