Conditional sentences are used to talk about real and unreal events. The real events are usually true or at least possible. The unreal events are usually hypothetical and can describe what could have happened or what we wish could have happened.
Conditionals consist of two clauses -- the "if" clause and the main clause. There are five types of conditionals:
Zero conditional 1st conditional 2nd conditional 3rd conditional Mixed conditional
With the zero conditional, both clauses use the present simple tense and the event is real and/or true.
If + present simple..., ... present simple...
If you don't finish your homework, you can't go to the park. If Judy creates the presentation, she must learn to use PowerPoint.
With the first conditional, the "if" clause uses the present simple tense and the main clause uses the future simple tense. The event is a real possibility.
If + present simple..., ...future simple...
If Tina comes in late one more time, she will get fired. If I don't get this account, I won't get that promotion.
With the second conditional, the “if” clause uses the past simple tense and the main clause uses would + verb. This conditional refers to an unreal event in the present or future.
If + past simple..., ... would (not) + verb...
If I had a million dollars, I would travel the world. (I don't have a million dollars, so I can't travel the world.)
If Ed hadn’t come in late to work today, Mr. Jensen wouldn’t be angry. (Ed did come in late so Mr. Jensen is angry.)
When using the verb be with the "if" clause for this conditional, you should use were instead of was for all subjects.
If I were older, I would be happier. If he were smart, he would stay late to finish his report.
If you want to increase the probability of the event, you can use could instead of would.
If I didn't have to go to this party, I could go to the movies with you. If Carl had more time, he could finish this report and go out with us tonight.
With the third conditional, the “if” clause uses the past perfect tense and the main clause uses would (not) have + past participle. This conditional refers to an unreal event in the past.
If + past perfect..., ... would (not) have + past participle...
If I had gone with you, I would have missed the phone call from my mother. (I didn't go with you, so I didn't miss the phone call from my mother.)
If Chelsea hadn’t taken the day off, I wouldn’t have worked so long today. (Chelsea did take the day off, so I did have to work long.)
With the mixed conditional, the "if" clause and the main clause refer to events that occur in different times.
Present result of a past condition
If + past perfect..., ... would (not) + verb...
If I had finished college, I would have a better job.
(I didn't finish college before, so I don't have a better job now.)
If you hadn't insulted the client, our company would be more profitable. (You did insult the client, so now our company is not profitable.)
Past result of a present or future condition
If + simple past..., ... would have + past participle
If we didn't want your business, you wouldn't be here.
(We do want your business. That's why you are here.)
If you ate more vegetables, you would feel better. (You don't eat vegetables. That's why you feel bad.)