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Grammar Level B1

Conditionals: Zero, First, Second, Third

The four English conditionals explained simply — zero, first, second, and third — with the form, real examples, common mistakes, and a quick exercise.

if this happens  ·  then that follows

A conditional sentence has two halves: an if-part (the condition) and a result. English has four main patterns. What changes between them is time and reality: a general fact, a real future possibility, an unreal present or future, or an unreal past. Get that idea and the verb forms follow.

The four patterns at a glance

Zero — if + present, present. A general truth. ("If you heat ice, it melts.")
First — if + present, usually will + verb. A real future possibility. ("If it rains, we'll stay in.")
Second — if + past, would + verb. Unreal or unlikely now. ("If I had time, I'd help.")
Third — if + past perfect, would have + participle. Unreal past. ("If I had known, I would have called.")

When the if-part comes first, put a comma after it. When the result comes first, no comma: We'll stay in if it rains.

Zero & first: real situations

Zero is for things that are always true — science, rules, habits. You can usually swap if for when.

If you don't water plants, they die. · If I drink coffee late, I can't sleep.

First is for a real, possible future. The if-part stays in the present even though it's about the future.

If you study tonight, you'll pass. · I'll call you if I need help.

The result part often uses will, but it can also use can, may, might, or an imperative: If it rains, take an umbrella.

Second & third: unreal situations

Second imagines the present or future differently from reality. The past tense here doesn't mean past time — it signals "this isn't real". With be, were is the safest standard form for all subjects: If I were you. In informal speech, was is also common with I/he/she, but were is better for careful English and exams.

If I won the lottery, I'd travel the world. · If I were you, I'd apologize.

Third imagines the past differently — something that didn't happen, often with regret.

If I'd studied, I would have passed. · We'd have caught the train if we had left earlier.

Common mistakes

Putting will in the if-part for a normal future condition.

✕If it will rain, we'll stay home.
✓If it rains, we'll stay home.

Use the present tense in the if-part when you mean a future condition. Will can appear in an if-part only in special meanings, such as willingness: If you'll wait here, I'll call him.

Putting would in the if-part for the imagined condition.

✕If I would have more money, I'd travel.
✓If I had more money, I'd travel.

For the imagined condition, use the past form: If I had more money. Would belongs in the result part: I'd travel. There are special cases where would in an if-part means willingness, but that is a different use.

Mixing up second and third. Second = unreal now; third = unreal past. "If I knew" (now) vs "If I had known" (in the past).

Quick exercise

Put the verb in the right form. Which conditional is it?

  1. If you ___ (mix) blue and yellow, you get green.
  2. If she ___ (call) me later, I'll tell her.
  3. If I ___ (be) taller, I'd play basketball.
  4. If they had left earlier, they ___ (catch) the bus.
  5. I'd buy that car if it ___ (be) cheaper.
Answer key
  1. mix — zero (general truth)
  2. calls — first (real future)
  3. were — second conditional; safest standard form with be
  4. would have caught — third (unreal past)
  5. were — second (unreal now)

Related topics

Will vs Going to: Talking About the Future Present Perfect vs Past Simple Since vs For with the Present Perfect

Practice this in Recursio

Conditionals click once you stop translating and start building them. Recursio's AI Coach drills each type — general facts, real future, unreal present/future, and unreal past — in short guided exercises, and the Daily Mixed Review brings the patterns back until "If I were you" comes out without thinking.

Practice grammar in Recursio →  ·  Free to start, on iOS and Android.