TOEFL Grammar: Verb complements and voice 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
Some verbs are followed by -ing, some by to, some by a bare verb; and the passive changes who appears as the subject. These patterns have to be learned verb by verb, and they show up constantly when you explain what someone decided, asked or allowed.
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. Gerund after a preposition When a verb follows a preposition, use its ing form.
Correct I am interested in joining the study group.
Common trap · incorrect I am interested in join the study group.
What goes wrong: the trap uses “join” where the correct sentence has “joining”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Academic Discussion
Sources: Prepositional phrases ; Word patterns: interested
2. Adjective plus infinitive Many adjective patterns use to plus a base verb to name the relevant action.
Correct It is important to check the deadline.
Common trap · incorrect It is important check the deadline.
What goes wrong: the trap leaves out “to”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Academic Discussion
Source: Dummy subjects
3. Enjoy plus gerund Use an ing form, not a to-infinitive, after enjoy.
Correct She enjoys studying in the library.
Common trap · incorrect She enjoys to study in the library.
What goes wrong: the trap uses “to study” where the correct sentence has “studying”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Academic Discussion
Source: Verb patterns: verb + infinitive or -ing
4. Decide plus infinitive Use to plus a base verb after decide when naming the chosen action.
Correct They decided to postpone the meeting.
Common trap · incorrect They decided postponing the meeting.
What goes wrong: the trap uses “postponing” where the correct sentence has “to postpone”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Academic Discussion
Source: Verb patterns: verb + infinitive or -ing
5. Ask someone to act Use an object followed by to plus a base verb after ask when requesting an action.
Correct I asked the tutor to explain the chart.
Common trap · incorrect I asked the tutor explain the chart.
What goes wrong: the trap leaves out “to”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Academic Discussion
Source: Verb patterns: verb + infinitive or -ing
6. Let plus base verb Use a base verb without to after let plus an object.
Correct The instructor let us leave early.
Common trap · incorrect The instructor let us to leave early.
What goes wrong: the trap adds “to”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Academic Discussion
Source: Verb patterns: verb + infinitive or -ing
7. Make plus base verb Use a base verb without to after make plus an object in an active causative clause.
Correct The delay made us wait outside.
Common trap · incorrect The delay made us to wait outside.
What goes wrong: the trap adds “to”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Academic Discussion
Source: Verb patterns: verb + infinitive or -ing
8. Basic passive form Use a form of be plus a past participle when the subject receives an action.
Correct The form was submitted yesterday.
Common trap · incorrect The form was submit yesterday.
What goes wrong: the trap uses “submit” where the correct sentence has “submitted”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Academic Discussion
Source: Active and passive voice
9. Passive agent by Use by to name the doer of an action in a passive clause.
Correct The map was drawn by the students.
Common trap · incorrect The map was drawn from the students.
What goes wrong: the trap uses “from” where the correct sentence has “by”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Academic Discussion
Source: Active and passive voice
10. Infinitive of purpose Use to plus a base verb to express the purpose of an action.
Correct I went to the library to print the article.
Common trap · incorrect I went to the library for print the article.
What goes wrong: the trap uses “for” where the correct sentence has “to”, so it no longer follows the rule.
Matters for: Build a Sentence · Write an Email · Academic Discussion
Source: Infinitive of purpose
Previous ← Clauses and connections Next Reference and comparison → Other grammar topics
Frequently Asked Questions Which TOEFL tasks test verb complements and voice? + No task names grammar topics, but these rules matter most in Build a Sentence, Write an Email, 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.