TOEFL Grammar: Conditionals and modality 10 hard-level rules, each shown with a correct sentence, the mistake learners most often make instead, and the TOEFL tasks where it counts.
Test Ninjas Research · Updated October 1, 2026
Unreal conditions, past inferences with must have and may have, and wishes. These structures let you discuss what might happen or might have happened, which is exactly what interview questions about hypothetical situations ask for.
Part of the
TOEFL grammar guide : 120 rules in 12 topics. The cards are original teaching material checked against the linked references; they are not an ETS syllabus.
The rules 1. Present unreal condition Use a past-form if-clause with would plus a base verb to discuss an unreal present situation.
Correct If I had more time, I would review the paper.
Common trap · incorrect If I would have more time, I would review the paper.
What goes wrong: the trap uses “would have” where the correct sentence has “had”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Take an Interview
Source: Conditionals: zero, first and second
2. Past unreal condition Use had plus a past participle in an if-clause about an unreal past event.
Correct If we had left earlier, we would have caught the shuttle.
Common trap · incorrect If we would have left earlier, we would have caught the shuttle.
What goes wrong: the trap uses “would have” where the correct sentence has “had”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Take an Interview
Source: Conditionals: third and mixed
3. Mixed past-to-present condition A past unreal condition can lead to a present unreal result with would plus a base verb.
Correct If I had studied the map, I would know the route now.
Common trap · incorrect If I had studied the map, I will know the route now.
What goes wrong: the trap uses “will” where the correct sentence has “would”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Take an Interview
Source: Conditionals: third and mixed
4. Unless with future result Use a present form after unless for an ordinary future condition.
Correct Unless you register, you will not be able to enter.
Common trap · incorrect Unless you will register, you will not be able to enter.
What goes wrong: the trap adds “will”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Take an Interview
Source: Unless
5. Must have for past inference Use must have plus a past participle for a strong inference about a past event.
Correct The door is locked; the custodian must have left.
Common trap · incorrect The door is locked; the custodian must has left.
What goes wrong: the trap uses “has” where the correct sentence has “have”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Take an Interview
Source: Modals: deductions about the past
6. May have for past possibility Use may have plus a past participle for an uncertain past possibility.
Correct The email may have gone to spam.
Common trap · incorrect The email may has gone to spam.
What goes wrong: the trap uses “has” where the correct sentence has “have”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Take an Interview
Source: Modals: deductions about the past
7. Should have for missed action Use should have plus a past participle to say an earlier action would have been advisable.
Correct I should have checked the room number.
Common trap · incorrect I should checked the room number.
What goes wrong: the trap leaves out “have”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Take an Interview
Source: Should
8. Wish about the present Use a past form after wish for an unreal present situation.
Correct I wish I knew the answer.
Common trap · incorrect I wish I know the answer.
What goes wrong: the trap uses “know” where the correct sentence has “knew”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Take an Interview
Source: Unreal time
9. Wish about the past Use had plus a past participle after wish for regret about an earlier event.
Correct I wish I had saved the draft.
Common trap · incorrect I wish I have saved the draft.
What goes wrong: the trap uses “have” where the correct sentence has “had”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Take an Interview
Source: Unreal time
10. Would rather plus base verb Use a base verb without to after would rather when stating a preference.
Correct I would rather meet on Friday.
Common trap · incorrect I would rather to meet on Friday.
What goes wrong: the trap adds “to”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Take an Interview
Source: Unreal time
Previous ← Advanced clause structure Next Academic cohesion and punctuation → Other grammar topics
Frequently Asked Questions Which TOEFL tasks test conditionals and modality? + No task names grammar topics, but these rules matter most in Build a Sentence, Write an Email, Take an Interview. Build a Sentence rewards correct word order and forms directly; in emails, discussion posts and spoken answers, errors here make your meaning harder to follow.
Are these official TOEFL grammar rules? + No. ETS does not publish a grammar syllabus. These are original Test Ninjas teaching cards based on standard English usage, with links to the reference pages each rule was checked against.
How should I practice these rules? + Read the rule, then cover the correct sentence and try to fix the trap yourself. Next, write one new sentence of your own that follows the rule, ideally about a campus or class situation.