Third Conditional
Conditional Form Use:
There are four common conditional forms in English; zero, first, second and third. The conditional communicates what happens, will happen, might have happened, or would have happened if we do, will do, or did do something. The situation described can be real or imaginary; in all the cases, an action depends on something else (a condition). For this reason, most English sentences in the conditional form include a dependent clause if.
The third conditional is used to talk about something that happened in the past. The third conditional explains that if (X) had happened, then (Y) would have happened. The third speaks something that can’t be changed because it happened in the past.
Example:
If she had known that you were in London, she would have phoned you.
She would have phoned you if she had known you were in London.
Note: The third person He/She/it doesn’t add S
Form
If + Past Perfect + Would/ Could/Should + Present Perfect Infinitive.
| Conditional Type | Use | If clause verb tense | Main clause verb tense |
| Zero | Basic truths | Simple present | Simple present |
| Type 1 | Possible condition with probable result | Simple present | Simple future |
| Type 2 | Hypothetical condition with probable result | Simple past | Present conditional or present continuous conditional |
| Type 3 | Unreal past condition with probable result in the past | Past perfect | Perfect conditional or perfect continuous conditional |
| Mixed | Unreal past or present condition with unreal past or present result | Past perfect or simple past | Present conditional or perfect conditional |