Conditional sentences talk about possible or imagined situations and their results. They usually contain the word if. For example: If it rains, we will stay at home.
English has four main types of conditional sentences, plus a mixed type. Each one uses a different tense pattern and has a different meaning. Learning these patterns helps you speak more naturally and score well in grammar exams.
This guide explains every type with simple rules, examples and a short practice exercise.
The Two Parts of a Conditional Sentence
- The if-clause (condition): If you study hard
- The main clause (result): you will pass
You can put either clause first. When the if-clause comes first, use a comma: If you study hard, you will pass. When the main clause comes first, no comma is needed: You will pass if you study hard.
Quick Summary Table
| Type | If-clause | Main clause | Use |
|---|---|---|---|
| Zero | present simple | present simple | general truths, facts |
| First | present simple | will + verb | real future possibility |
| Second | past simple | would + verb | unreal or unlikely present/future |
| Third | past perfect | would have + past participle | unreal past |
| Mixed | past perfect | would + verb | past condition, present result |
Zero Conditional
Form: If + present simple, present simple
Use: for facts, scientific truths and things that always happen.
- If you heat ice, it melts.
- If you mix red and blue, you get purple.
- If I drink coffee at night, I can’t sleep.
In zero conditionals, you can usually replace if with when without changing the meaning.
First Conditional
Form: If + present simple, will + base verb
Use: for real and likely situations in the future.
- If it rains tomorrow, the match will be cancelled.
- If you leave now, you will catch the bus.
- If she doesn’t study, she won’t pass.
Common mistake: Do not use will in the if-clause. Say If it rains, not If it will rain.
You can also use can, may, might or an imperative in the main clause: If you see Rahim, tell him to call me.
The British Council explains how verbs work after if and time words like when in its page on verbs in time clauses and if clauses.
Second Conditional
Form: If + past simple, would + base verb
Use: for imaginary, unlikely or impossible situations in the present or future.
- If I had a lot of money, I would travel the world.
- If I were you, I would apologise.
- If he lived closer, he would visit more often.
Even though the verb is in the past tense, the meaning is about now or the future. The past tense shows that the situation is not real.
If I were: In formal English, use were for all subjects: If I were, if she were, if it were. In casual speech, people often say if I was, but were is safer in exams.
Third Conditional
Form: If + past perfect, would have + past participle
Use: for imaginary situations in the past. Often used for regrets or criticism.
- If I had studied harder, I would have passed the exam. (But I didn’t study, so I failed.)
- If we had left earlier, we would have caught the train.
- If she hadn’t helped me, I would have been lost.
The past cannot change, so third conditionals always describe something that did not happen.
Mixed Conditionals
Mixed conditionals combine two different times.
Past Condition, Present Result
Form: If + past perfect, would + base verb
- If I had taken the job, I would be rich now.
- If she had learned English as a child, she would speak it fluently today.
Present Condition, Past Result
Form: If + past simple, would have + past participle
- If I weren’t so shy, I would have spoken at the meeting.
Other Ways to Express Conditions
Unless
Unless means if not.
You will fail unless you study. = You will fail if you don’t study.
Provided that / As long as
You can go out as long as you finish your homework.
Inversion (Formal)
In formal English, we can drop if and invert the subject and verb:
- Had I known, I would have helped. (= If I had known)
- Were I you, I would accept. (= If I were you)
- Should you need help, call me. (= If you need help)
This advanced form is explained in the British Council’s lesson on inversion and conditionals.
Common Mistakes
| Wrong | Right |
|---|---|
| If I will see him, I will tell him. | If I see him, I will tell him. |
| If I would have money, I would buy it. | If I had money, I would buy it. |
| If I had known, I would told you. | If I had known, I would have told you. |
| Unless you don’t hurry, you will be late. | Unless you hurry, you will be late. |
Practice Exercise
Complete the sentences with the correct form of the verb in brackets.
- If you ___ (boil) water, it ___ (turn) into steam.
- If it ___ (be) sunny tomorrow, we ___ (go) to the beach.
- If I ___ (be) a bird, I ___ (fly) over the mountains.
- If they ___ (invite) me, I ___ (come) to the party. (past, but they didn’t)
- You won’t get better unless you ___ (take) your medicine.
- If she ___ (save) money last year, she ___ (have) a new phone now.
Answers
- boil, turns (zero)
- is, will go (first)
- were, would fly (second)
- had invited, would have come (third)
- take
- had saved, would have (mixed)
For extra practice and reference, see Purdue OWL’s free grammar resources.
Frequently Asked Questions
How many types of conditional sentences are there?
There are four main types (zero, first, second and third) plus mixed conditionals.
Which conditional is used for impossible situations?
The second conditional is used for impossible or unlikely present situations. The third conditional is used for impossible past situations.
Can I use “will” after “if”?
Usually not. Use the present simple after if for future meaning: If it rains, not If it will rain.
Conclusion
Conditional sentences follow clear patterns. Zero is for facts, first is for real future possibilities, second is for imaginary present situations, and third is for imaginary past situations. Mixed conditionals connect past and present.
Because conditionals depend on tenses and clauses, it helps to review English tenses and their uses and what a clause is. For structured practice, see our review of English Grammar in Use Intermediate.
