Grammar / usage: Conditional sentences
Subtopic: Section D · Grammar
How to structure your answer
Rule: English conditionals come in four main patterns. Zero conditional ('If you heat water, it boils') states a general truth — present in both clauses. First conditional ('If it rains, we will stay') is open — present in the if-clause, future in the main clause. Second conditional ('If I had time, I would help') is hypothetical — past in the if-clause, would + infinitive in the main clause. Third conditional ('If I had known, I would have helped') is counterfactual about the past — past perfect in the if-clause, would have + past participle in the main clause.
Approach: identify the kind of condition being expressed — habitual truth, real future possibility, present unreality, or past unreality — and match the pattern. Never use 'will' or 'would' in the if-clause itself.
What an examiner expects: the four patterns named cleanly; corrected sentences with the verb forms underlined; a one-line justification.
Common pitfalls: (1) using 'will' in the if-clause of a first conditional ('If he will come, I will help'); (2) mixing second and third conditional forms; (3) using 'was' instead of 'were' after 'if I' in the formal hypothetical ('If I were you').
Detailed model answer
118 words · target 100 words · 8 min
Rule: Conditional sentences pair an if-clause with a result clause. Type 1 (real future): present + will/may. Type 2 (unreal present): past + would. Type 3 (unreal past): past perfect + would have.
Worked examples: 'If it rains, the match will be cancelled' (type 1). 'If I were the chief minister, I would reform schools' (type 2). 'If she had studied, she would have passed' (type 3 — fact contrary to past reality).
Quick check:
- If he (works/will work) hard, he will succeed. works
- If I (was/were) you, I would apologise. were
- If they had left earlier, they (would catch/would have caught) the train. would have caught
- She would help us if she (has/had) the time. had
- Unless you (hurry/will hurry), you'll miss the bus. hurry
What an examiner expects to see
- Zero conditional: 'If + present, present' — general truth.
- First conditional: 'If + present, will + infinitive' — open future.
- Second conditional: 'If + past, would + infinitive' — present unreality.
- Third conditional: 'If + past perfect, would have + past participle' — past unreality.
- Never use 'will' or 'would' in the if-clause.
- Use 'were' (not 'was') with 'I/he/she/it' in the formal hypothetical ('If I were you').
- Mixed conditional: past condition with present result ('If I had studied, I would be a doctor today').
- 'Unless' = 'if not' and takes the same verb forms.
- 'Provided that', 'as long as', 'on condition that' behave like 'if'.
- Practice sentences for the examinee to correct.
Concrete cases, schemes and judgments
- Wrong: 'If he will come, I will help.' Right: 'If he comes, I will help.' (first conditional — present in if-clause.)
- Wrong: 'If I was rich, I would travel.' Right: 'If I were rich, I would travel.' (formal hypothetical takes 'were'.)
- Wrong: 'If I would have known, I would have helped.' Right: 'If I had known, I would have helped.' (third conditional — past perfect, then would have.)
- Wrong: 'Unless you will study, you will fail.' Right: 'Unless you study, you will fail.' ('Unless' = 'if not' — no 'will' in the if-clause.)