The third conditional is about something that did not happen in the past and its imaginary result: If + Past Perfect (had + past participle), would have + past participle. If people had planted more trees, the valley would have stayed greener. It expresses regret or criticism, because the action is finished and cannot be changed. Global warming is the long-term rise in Earth’s average temperature; one major cause is the burning of coal, oil and gas, which releases greenhouse gases such as carbon dioxide. Do not mix up the second and third conditionals: If I had a car, I would drive (I have no car now); If I had had a car, I would have driven (I had none then).
Worked examples
If the factory had installed filters, the river would not have turned grey.
If the ice had not melted so quickly, the polar bear would have found food nearby.
Class activity
“Regret chain”: one student states a regret (I didn’t save my work) and a partner answers with the third conditional (If you had saved it, you wouldn’t have lost it).
Practice
1
Complete: If we ___ (leave) earlier, we ___ (not / miss) the train.
had left; would not have missed
2
Make a third conditional sentence: the farmer / not water the field / the crop / die. (Use the real past: he did not water; the crop died.)
If the farmer had watered the field, the crop would not have died.
3
Is this sentence second or third conditional? “If glaciers had stayed stable, sea levels would not have risen.”
Third conditional, because it talks about the unreal past.
4
Why is the third conditional often used to express regret?
Because it describes a past action that cannot be changed, so we can only imagine a different result.