Sentences with 'if': A conditional sentence talks about a condition and its result: "If something happens, then something else happens." It has two halves — the if-clause (the condition) and the main clause (the result).
English has four conditionals. The one you choose depends on how real or likely the situation is — from a general truth, to a real future, to an imaginary present, to an impossible past.
- conditional
- a sentence that links a condition to its result, usually using 'if'
- if-clause
- the half that gives the condition ("If it rains…")
- main clause / result clause
- the half that gives the result ("…we'll stay in")
- zero conditional
- for general truths and facts (if + present, present)
- first conditional
- for a real, likely future situation (if + present, will + base verb)
- second conditional
- for an unreal or unlikely present/future (if + past, would + base verb)
- third conditional
- for an unreal, impossible past (if + past perfect, would have + past participle)
- unless
- a way to say 'if not' ("Unless you hurry, you'll be late")
Why it carries the marks: Conditionals show off a range of tenses and structures — exactly what Criterion A (Language) rewards. A confident "If I were you, I would…" or "If I had known, I would have…" lifts a written answer or oral above the safe present-tense level. Examiners notice the wrong form ("If I will…") immediately, so the patterns are worth learning precisely.
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Four patterns, one logic: Each conditional pairs a tense in the if-clause with a structure in the main clause. The key idea: the less real the situation, the further back the tense moves.
Golden rule: never put will or would in the if-clause. Write "If it rains…" (not "If it will rain…") and "If I had time…" (not "If I would have time…").
| Type | If-clause | Main clause | Example |
|---|---|---|---|
| Zero | present simple | present simple | If you heat ice, it melts. |
| First | present simple | will + base verb | If it rains, we will stay in. |
| Second | past simple | would + base verb | If I won the lottery, I would travel. |
| Third | past perfect | would have + past participle | If I had left earlier, I would have caught the bus. |
Two handy details: 1. 'were' for everyone (2nd conditional). In careful English we use were for all subjects: "If I were you, I would apologise." ("If I was…" is common in speech but "were" is the exam-safe form.)
2. Contractions. The result clause is usually contracted: "we 'll stay" (first), "I 'd travel" (second), "I 'd have caught" (third). Both the full and contracted forms are correct.
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How real is the idea?: Choosing the right conditional is really one question: how real is the situation? A fact you can always rely on → zero. Something that may genuinely happen → first. Something imaginary or unlikely now → second. Something that did not happen in the past → third.
Which one to use
- Zero — a general truth or rule: "If you don't water plants, they die."
- First — a real future possibility: "If I finish my homework, I'll watch a film."
- Second — an imaginary/unlikely present + advice with 'If I were you…': "If I were you, I'd take the earlier train."
- Third — regret or a different past: "If we had booked earlier, the flight would have been cheaper."
- Unless = 'if not': "You'll miss the bus unless you leave now."
Real / possible
- Zero — always true: "If you press this, the light comes on."
- First — could really happen: "If she calls, I'll answer."
Unreal / imaginary
- Second — not the case now: "If I lived by the sea, I'd swim every day."
- Third — didn't happen: "If you had told me, I would have helped."
Comma rule (word order): Either clause can come first. When the if-clause comes first, put a comma between the clauses: "If it rains, we'll stay in." When the main clause comes first, you need no comma: "We'll stay in if it rains." The meaning is the same.
All four, one after another: Here are the four conditionals built up step by step around a single idea. Watch how the tense moves further back as the situation becomes less real, while the result clause climbs from get/comes → will → would → would have.
IB-style task — the four conditionals in action
From general truth to impossible past
- Zero conditional (a general truth): "If you mix blue and yellow, you get green." — both verbs are in the present, because this is always true.
- First conditional (a real future possibility): "If it rains tomorrow, we'll cancel the trip." — if + present, then will + base verb.
- Second conditional (an unreal or unlikely present): "If I had more time, I would learn the piano." — if + past, then would + base verb.
- Third conditional (an unreal past): "If I had studied harder, I would have passed the exam." — if + past perfect, then would have + past participle.
- Notice the pattern: the further from reality the idea is, the further 'back' the tense moves — present → past → past perfect — while the result clause climbs will → would → would have.
Steal this for your writing: You don't need all four in every answer — but slipping in one well-formed second or third conditional ("If I were…, I would…" / "If I had known…, I would have…") signals a strong command of structure. Plan one in advance for your oral or a Paper 1 task.
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The slips to watch for: Three mistakes dominate. 1. Putting will/would in the if-clause ("If it will rain…"). 2. Mixing up the two halves of a conditional ("If I had time, I will help" — should be would). 3. Forgetting the comma when the if-clause comes first. Compare the right version with the typical mistake and the fix becomes obvious.
Correct
- If it rains, we'll stay in.
- If I had more money, I would travel.
- If I had known, I would have called you.
Common mistake
- If it will rain, we'll stay in. (no 'will' in the if-clause → if it rains)
- If I would have more money, I would travel. (no 'would' in the if-clause → if I had)
- If I had known, I would called you. (third needs 'would HAVE called')
Ask: how real, and is each half correct?: Before you write a conditional, do two quick checks. 1. Decide how real the idea is (fact → first → second → third) so you pick the right type. 2. Make sure the two halves match the pattern — and keep will/would out of the if-clause. If the if-clause comes first, add the comma.