If I had known... I wish I had known...

This lesson explains how to talk about past regrets and unreal past situations using the third conditional and the phrase 'I wish I had known...'. These structures let you describe things that did not happen and how you would have acted differently.

• Use the third conditional (If + past perfect, would have + past participle) for unreal past situations and their imagined results.
• Use 'I wish I had known...' to express regret about something you did not know in the past.
• Both forms refer to events that cannot be changed—only imagined outcomes.

Remember the exact forms and when to use them:

• Third conditional: If + past perfect, would have + past participle → to imagine a different past outcome.
• 'I wish I had known...' uses wish + past perfect to express regret about not knowing something in the past.
• Use 'had known' (not 'knew') in these structures because they refer to unreal past situations.

Think: both forms refer to past facts that are not true — use past perfect.

Watch out for these universal errors when using third conditional and wish + past perfect:

• Using 'would' (or 'would have') in the if-clause: incorrect → If I would have known...
• Using simple past instead of past perfect in the if-clause: incorrect → If I knew..., in this context you need past perfect.
• Mixing tenses incorrectly in result clause: keep result as would have + past participle.
• Using 'wish' with present forms for past regrets: avoid 'I wish I knew' when you mean a past regret — use 'I wish I had known.'

Focus on tense sequence: past perfect in the if-clause or after wish; would have in the result.