- If + present simple, .... present simple.
This conditional is used when the result will always happen. So, if water reaches 100 degrees, it always boils. It's a fact. I'm talking in general, not about one particular situation. The result of the 'if clause' is always the main cluase.
The 'if' in this conditional can usually be replaced by 'when' without changing the meaning.
- If you freeze water, it turns into ice.
- If I work too much, I get tired.
- If they come here, they always bring a present.
- If she doesn't know the answer, she keeps silent.
- If we don't go out on Saturdays, we rent a video and stay home.
The first conditional has the present simple after 'if', then the future simplein the other clause:
- if + present simple, ... will + infinitive
It's used to talk about things which might happen in the future. Of course, we can't know what will happen in the future, but this describes possible things, which could easily come true.
- If he is busy now, I will come back tomorrow.
- If it is warm tomorrow, we'll go to the beach.
- If it is cold, you must wear warm clothes.
- If she doesn't call you, you can call her.
- If you work hard, you may become a millonaire someday.
The second conditional uses the past simple after if, then 'would' and the infinitive:
- if + past simple, ...would + infinitive
(We can use 'were' instead of 'was' with 'I' and 'he/she/it'. This is mostly done in formal writing).
- If you went to Brazil, you wouldn't want to come back.
- If he didn't live by the river, he couldn't go fishing.
- If I didn't want to go, I would tell you.
- If they worked for that company, they might have better salaries.
- If she wrote a book, it would be a best-seller.
We make the third conditional by using the past perfect after 'if' and then 'would have' and the past participle in the second part of the sentence:
- if + past perfect, ...would + have + past participle
It talks about the past. It's used to describe a situation that didn't happen, and to imagine the result of this situation.
- If they had invited us, we would have accepted at once.
- If she had explained me the problem, I would have understood it.
- If it hadn't rained, we would have gone fishing.
- If my sister had been here, she would have enjoyed this.
- If he had worked more, he could have saved more money.