There are 3 types of conditional sentences, each with their own forms.
Conditional Sentence Type 0
Used to talk about general truths, scientific facts, or things which always happen under certain conditions.
The form is as follow:
If + Simple present + Simple present
If you cross an international dateline, the time changes. (facts)
Phosphorus burns if you expose it to air. (facts)
If I wake up early, I go jogging. (actions that will happen)
**Note: You can also use when instead of if.
Conditional Sentences Type 1
Often called the "real" conditional because it is used for real or possible situations. These situations take place if a certain condition is met. It is possible and also very likely that the condition will be fulfilled.
If + Simple present + Simple future
If I have enough time, I’ll watch the football game.
I may have time to watch the show but I’m not entirely sure about it.
Conditional Sentence Type 2
Often called the "unreal" conditional because it is used for unreal impossible or improbable situations. This conditional provides an imaginary result for a given situation. It is very unlikely that the condition will be fulfilled.
If + Simple past + would + base verb
Were/was
In conditional type 2, we usually use were" instead of "was" in the if clause " even if the pronoun is I, he, she or it.
**Note: was is also a possible form.
If I were a millionaire, I would buy a castle
Conditional sentence type 2 also refers to an action in the present that could happen if the present situation were different.
If I had a lot of money, I would travel around the world.
Conditional Sentence Type 3
It is impossible that the condition will be met because it refers to the past.
If + Past perfect + would + have + Past participle
If he had been careful, he wouldn’t have had that accident.
(this event happened in the past as the driver was careless so the accident was had)
Assess yourself by staged practices