Third Conditional: unreal past, unreal past result

The Third Conditional talks about a past that cannot be changed. Both parts are unreal: the condition did not happen, so the result did not happen either. The if-clause can come first (with a comma) or second.

If + had + past participle, would have + past participle

• If she had seen the warning, she would have stopped.
• If we hadn't changed the supplier, we would have lost the client.
• I would have called you if I had known your number.

Mixed conditional: unreal past, present result

A past decision often still matters today. When the unreal condition is in the past but its imagined result is now, keep if + Past Perfect and change the result to would + base verb, or would be + -ing for something in progress now.

If + had + past participle, would + base verb / would be + -ing

• If she had learned to drive, she wouldn't need a lift every day.
• If I hadn't changed career, I would still be working in a bank.
• If they had reconsidered the offer, they would be our partners today.

Time words show the present result: now, today, still, at the moment.