Câu điều kiện ("If" sentence)

A. Câu điều kiện loại I (the conditional sentence type I)
1. Cấu trúc
Clause 1 (the simple future) + if + Clause 2 (the simple present)
2. Cách sử dụng và ví dụ
– Diễn tả sự việc có thể xảy ra ở hiện tại hoặc tương lai.
Ví dụ:
I’ll visit Ho Chi Minh city if I have time.
We’ll pass the exam if we work hard.
3. Các biến thể cơ bản
Clause 1 (might/do +V) + if + Clause 2 (the simple present)
→ để chỉ khả năng khách quan
Ví dụ: It’s sunny. We may get a headache if we go out without a hat.

Clause 1 (may/can + V) + if + Clause 2 (the simple present)
→ để chỉ sự cho phép
Ví dụ: You can go home if you finish your test.

Clause 1 (must/should + V) + if + Clause 2 (the simple present)
→ để chỉ yêu cầu, đề nghị.
Ví dụ: You must do exercises if you want to get good marks.
4. If….not…= Unless
Ví dụ:
- I won’t visit you if I don’t have time
→ Unless I have time, I won’t visit you.
- We’ll go camping if the weather is fine.
→ Unless the weather is fine, we won’t go camping.
- If you miss seeing the first part of the film, you can’t say you understand it.
→ Unless you see the first part of the film, you can’t say you understand it.
Chú ý: mệnh đề chứa “unless” không dùng dạng phủ định.
B. Câu điều kiện loại II (the conditional sentence type II)
1. Cấu trúc
Clause 1 (would + V) + if + Clause 2 (the simple past tense)
2. Cách sử dụng và ví dụ
– Diễn tả sự việc không có thật ở hiện tại hoặc tương lai
Ví dụ:
If it were cold now, we wouldn’t switch on the fans.
(but it’s hot and we have to switch on the fans)
I would fly if I were a bird.
(but I am not a bird and I can’t fly)
Chú ý: Chúng ta dùng “were” cho tất cả các ngôi, không dùng “was”
3. Các biến thể cơ bản
Clause 1 (might/ could + V) + if + Clause 2 (the simple past tense)
→ chỉ khả năng
Ví dụ: He might succeed if he tried
I could speak French well if I lived in France.
C. Câu điều kiện loại III (the conditional sentence type III)
1. Cấu trúc cơ bản
Clause 1 (would have + P2) + if + Clause 2 (the past perfect)
2. Cách sử dụng và ví dụ
– Câu điều kiện loại III là câu điều kiện không có thật ở quá khứ.
Ví dụ:
a. Miss Phuong wouldn’t have won the prize if she hadn’t attended the beauty contest.
(but the fact that she attended and she won the prize)
b. We would have got good marks if we had prepared our last lesson carefully.
(but the fact that we didn’t prepare our last lesson carefully and we didn’t get good marks).
3. Các biến thể cơ bản
Clause 1 (could have + P2) + if + Clause 2 (had + P2)
→ chỉ sự chủ quan, sự cho phép.
Ví dụ:
I could have won a prize if I had taken part in the competition last week.
You could have gone to the cinema if you had finished your homework last night.

Clause 1 (might have + P2) + if + Clause (had + P2)
→ chỉ khả năng khách quan.
Ví dụ: The last crop might have been better if it had rained much.
D. Câu điều kiện hỗn hợp II, III (the mixed conditional sentence type II and III)
1. Cấu trúc cơ bản
Clause 1 (would + V) + if + Clause 2 (had + P2)
2. Ví dụ:
If I had been born in town, I would like life there.
(the fact that I wasn’t born in town, so I don’t like life there now)
If I followed your advice, I would have a job now.
(the fact that I didn’t follow your advice, so I don’t have a job now)
3. But for + noun + điều kiện loại II, III
But for: nếu không có…
Ví dụ:
You help me everyday so I can finish my work.
→ But for your daily help, I couldn’t finish my work.
She encouraged him and he succeeded.
→ But for her encouragement, he wouldn’t have succeeded.
The teacher explained and we understood.
→ But for the teacher’s explanation, we wouldn’t have understood.
E. Đảo ngữ của câu điều kiện
1. Điều kiện loại I
• Nếu trong câu có “should” ở mệnh đề if, thì đảo “should” lên đầu câu
If he should ring , I will tell him the news.
→ Should he ring, I will tell him the news.
• Nếu trong câu không có “should”, chúng ta phải mượn “should”
If he has free time, he’ll play tennis.
→ Should he have free time, he’ll play tennis.
If she comes early, we’ll start.
→ Should she come early, we’ll start.
2. Điệu kiện loại II
• Nếu trong câu có động từ “were”, thì đảo “were” lên đầu.
If I were a bird, I would fly.
→ Were I a bird, I would fly.
They would answer me if they were here.
→ Were they here, they would answer me.
• Nếu trong câu không có động từ “were” thì mượn “were’ và dùng “ to V”
If I learnt Russian, I would read a Russian book.
→ Were I to learn Russian, I would read a Russian book.
If they lived in Australia now, they would go swimming.
→ Were they to live in Australia now, they would go swimming.
3. Điều kiện loại III
• Đảo trợ động từ của thì quá khứ hoàn thành.
If it had rained yesterday, we would have stayed at home.
→ Had it rained yesterday, we would have stayed at home.
If he had trained hard, he would have won the match.
→ Had he trained hard, he would have won the match.
Chú ý: ở dạng phủ định, “not” được đặt sau chủ ngữ:
Had it not been so late, we would have called you.