Third conditional
仮定法過去完了（第3条件文）
形
- If + S + had + V3, S + would have + V3
- S + wouldn't have + V3 + if + S + hadn't + V3
- could/might have + V3
解説
過去の事実に反する仮定（「あのとき〜していたら…だっただろう」）を表します。if節は had + 過去分詞、主節は would have + 過去分詞。if節に would have を入れるのはよくある誤りです。
I'd known の 'd = had、I'd have の 'd = would。
例文
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If I had studied harder, I would have passed the exam.
もっと勉強していたら、試験に受かっていただろう。
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We wouldn't have got lost if we had taken a map.
地図を持っていっていたら、道に迷わなかっただろう。
-
If you had told me, I could have helped you.
言ってくれていたら、手伝えたのに。