Complex conditionals
Mix time references, invert conditionals and use formal alternatives to 'if'.
20 minAdvanced
1The grammar
Mixed conditionals combine different times. A past condition can have a present result: 'If we had invested earlier, we would be stronger now.' A present or general condition can have a past result: 'If she were not so careful, she would have missed the error.'
Formal conditionals can drop 'if' and invert the subject and auxiliary. Three forms are used: 'Had I known ...', 'Were we to proceed ...' and 'Should you require ...'. A negative stays uncontracted, with 'not' after the subject: 'Had we not acted ...'.
Several expressions can replace 'if': 'provided (that)', 'as long as', 'on condition that', 'unless', 'supposing', 'but for' and 'were it not for / had it not been for'. 'Unless' means 'except if', so it does not usually combine with another negative in the same clause.
2Structure and formation
Past condition, present result
If + past perfect, would + base verb
If he had taken the post, he would be in Brussels now.
Present condition, past result
If + past simple, would have + past participle
If they spoke German, they would have won the contract.
Inverted past condition
Had + subject + past participle, would have + past participle
Had the data been checked, the error would have been found.
Inverted unreal condition
Were + subject + to + base verb, would + base verb
Were the firm to relocate, hundreds of jobs would go.
Inverted possible condition
Should + subject + base verb, imperative / will + base verb
Should the offer change, we will let you know.
3Examples
If the bank had not been rescued in 2008, many of its customers would be far worse off today.
A past condition is linked to a present result.
If she were not so cautious, she would have invested in the start-up years ago.
A permanent characteristic explains a past result.
Had the report been published sooner, the policy might have changed.
An inverted past condition; 'might' shows that the result is less certain.
Were the central bank to raise rates again, mortgage defaults would increase.
'Were ... to' presents a hypothetical future event.
Should you wish to appeal, you must do so within fourteen days.
'Should' at the start is a formal way of presenting a possibility.
But for the intervention of the court, the building would have been demolished.
'But for' + noun means 'if it had not been for'.
Provided that the budget is approved, construction will begin in June.
'Provided that' stresses a necessary condition.
4Common mistakes
If I would have known, I would have acted.
If I had known, I would have acted.
Standard English uses the past perfect in the if-clause; 'would have' here is heard in casual speech but is not accepted in formal writing.
Was I in charge, I would change the policy.
Were I in charge, I would change the policy.
Inverted conditionals use 'were' for all subjects; 'was' is not used in this structure.
Hadn't we acted, the firm would have failed.
Had we not acted, the firm would have failed.
Inverted conditionals are not contracted; 'not' goes after the subject.
Should you will need help, please call.
Should you need help, please call.
'Should' is followed by the base form of the verb, not by 'will'.
5Practical usage
Formal letters and notices
'Should you have any questions, please contact us' is a standard polite phrase in business correspondence.
Analysis and argument
Mixed conditionals are useful when explaining how past decisions affect the present: 'If the state had invested in housing, rents would be lower today.'
Now practise it
Create a free account for 10 exercises on Complex conditionals, a final check, and an AI teacher who explains every mistake.