Third conditional

Rules

• Rule 1: If + had + V3

  The if-part uses the past perfect: had + V3 (negative: hadn't + V3). No would here.

  Pattern: If + subject + had / hadn't + V3

  Example: If you had called me, …

  Example: If the train hadn't stopped, …

• Rule 2: Result → would have + V3

  The result uses would have + V3 (negative: wouldn't have). Use could have for ability and might have for possibility.

  Pattern: subject + would / could / might have + V3

  Example: If she had trained harder, she would have won the race.

  Example: If we had known, we could have helped you.

• Rule 3: What really happened?

  The third conditional always says the opposite of reality. A positive clause means it didn't happen; a negative clause means it did.

  Pattern: If I had … → really: I didn't …

  Example: If I had brought my camera, I would have taken photos.

  Example: If it hadn't snowed, the school wouldn't have closed.

• Rule 4: Watch the contractions

  Both parts can use 'd, but in the if-part 'd = had, and in the result 'd = would. In speech, would have sounds like would've.

  Pattern: If I'd (had) known, I'd (would) have come.

  Example: If we'd left earlier, we'd have caught the ferry.

  Example: I would've helped if you'd asked.

Common mistakes

• If I would have known, I would have come. → If I had known, I would have come.

  No would in the if-part.

• If she had asked, I would helped her. → If she had asked, I would have helped her.

  Don't forget have: would have + V3.

• If we had went there, … → If we had gone there, …

  After had use the V3: gone.