1. 與現在事實相反的虛擬：,If + did / were + ..., ... would/ should/ could/ might + do (動詞原形),If I were you, I would go abroad at once. (I am not you.),If he knew it now, he could help me. (He doesn't know it now.),
2. 與過去事實相反的虛擬：,If + had done + ..., ... would (might) have done ...,If I had known your telephone number yesterday, I would have phoned you. (I didn't know your telephone number.),If you had e here a little earlier just now, you might have met her. (You didn't e here earlier.)
3. 與將來事實相反的虛擬：
,(1) If + should + v., ... would + v. (可能性很小)(譯作“萬一”),If it should rain tomorrow, you could stay at home.,If I should fail, what should I do?
(2) If + did / were to + v ..., would + v. (完全不可能),If the sun were to rise in the west, I would lend you the money.,If you finished it in 3 minutes, I would give you my car.
虛擬語氣主要有與現在事實相反、與過去事實相反、與將來事實相反的虛擬，以及幾種特殊情況，should、wish等虛擬語氣。
1. 與現在事實相反的虛擬：,If + did / were + ..., ... would/ should/ could/ might + do (動詞原形),If I were you, I would go abroad at once. (I am not you.),If he knew it now, he could help me. (He doesn't know it now.),
2. 與過去事實相反的虛擬：,If + had done + ..., ... would (might) have done ...,If I had known your telephone number yesterday, I would have phoned you. (I didn't know your telephone number.),If you had e here a little earlier just now, you might have met her. (You didn't e here earlier.)
3. 與將來事實相反的虛擬：
,(1) If + should + v., ... would + v. (可能性很小)(譯作“萬一”),If it should rain tomorrow, you could stay at home.,If I should fail, what should I do?
(2) If + did / were to + v ..., would + v. (完全不可能),If the sun were to rise in the west, I would lend you the money.,If you finished it in 3 minutes, I would give you my car.