TOEFL Grammar: Clauses and connections 10 medium-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
Because versus because of, although versus despite, who versus which: these words join ideas, and each needs a particular kind of phrase after it. They are central to developing a reason in the Academic Discussion task and to arranging longer sentences in Build a Sentence.
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. Because plus clause Follow because with a subject and verb when giving a reason.
Correct We left because the lab closed.
Common trap · incorrect We left because the lab closing.
What goes wrong: the trap uses “closing” where the correct sentence has “closed”, so it no longer follows the rule.
Matters for: Build a Sentence · Academic Discussion
Source: Word patterns: because or because of
2. Because of plus noun phrase Follow because of with a noun phrase rather than a finite clause.
Correct The event moved because of the rain.
Common trap · incorrect The event moved because of it rained.
What goes wrong: the trap uses “it rained” where the correct sentence has “the rain”, so it no longer follows the rule.
Matters for: Build a Sentence · Academic Discussion
Source: Word patterns: because or because of
3. Although without but Do not add but to the main clause when although already marks the contrast.
Correct Although the task was short, it was difficult.
Common trap · incorrect Although the task was short, but it was difficult.
What goes wrong: the trap adds “but”, so it no longer follows the rule.
Matters for: Build a Sentence · Academic Discussion
Source: Conjunctions: contrasting
4. Despite plus noun phrase Follow despite with a noun phrase or an ing phrase, not a plain finite clause.
Correct Despite the delay, we finished.
Common trap · incorrect Despite it was delayed, we finished.
What goes wrong: the trap uses “it was delayed” where the correct sentence has “the delay”, so it no longer follows the rule.
Matters for: Build a Sentence · Academic Discussion
Source: Contrasting ideas: although, despite and others
5. Who for a person Use who as the subject of a relative clause about a person.
Correct The student who designed the chart spoke first.
Common trap · incorrect The student which designed the chart spoke first.
What goes wrong: the trap uses “which” where the correct sentence has “who”, so it no longer follows the rule.
Matters for: Build a Sentence · Academic Discussion
Source: Relative clauses: defining and non-defining
6. Which or that for a thing Use which or that, not who, for a relative clause about a thing.
Correct The method that reduced errors was adopted.
Common trap · incorrect The method who reduced errors was adopted.
What goes wrong: the trap uses “who” where the correct sentence has “that”, so it no longer follows the rule.
Matters for: Build a Sentence · Academic Discussion
Source: Relative clauses: defining and non-defining
7. Whose for possession Use whose to link a person or thing to something it possesses.
Correct The professor whose article we read is speaking.
Common trap · incorrect The professor who article we read is speaking.
What goes wrong: the trap uses “who” where the correct sentence has “whose”, so it no longer follows the rule.
Matters for: Build a Sentence · Academic Discussion
Source: Whose
8. Embedded question order Inside a longer question, use statement order in the embedded clause.
Correct Could you tell me where the workshop is?
Common trap · incorrect Could you tell me where is the workshop?
What goes wrong: the trap uses the same words in a different order, so it no longer follows the rule.
Matters for: Build a Sentence · Academic Discussion
Source: Word order: where
9. That-clause order After that introduces a content clause, keep its subject before its verb.
Correct We know that the library is open.
Common trap · incorrect We know that is the library open.
What goes wrong: the trap uses the same words in a different order, so it no longer follows the rule.
Matters for: Build a Sentence · Academic Discussion
Source: That-clauses
10. Future if-clause For an ordinary possible future condition, use a present form in the if-clause and place will in the result clause.
Correct If the office opens early, I will visit.
Common trap · incorrect If the office will open early, I will visit.
What goes wrong: the trap uses “will open” where the correct sentence has “opens”, so it no longer follows the rule.
Matters for: Build a Sentence · Academic Discussion
Source: Will and would
Previous ← Time and aspect Next Verb complements and voice → Other grammar topics
Frequently Asked Questions Which TOEFL tasks test clauses and connections? + No task names grammar topics, but these rules matter most in Build a Sentence, Academic Discussion. 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.