TOEFL Grammar: Nouns and determiners 10 easy-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
Small words in front of nouns — a, an, the, this, many — and the endings on the nouns themselves carry a lot of information. They decide whether you mean one thing or several, a specific thing or any thing. In Complete the Words, a missing plural ending or article is often exactly what you have to restore.
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. Singular count nouns A singular count noun usually needs a determiner such as a, the, or this.
Correct I need a pencil for the diagram.
Common trap · incorrect I need pencil for the diagram.
What goes wrong: the trap leaves out “a”, so it no longer follows the rule.
Matters for: Complete the Words · Build a Sentence · Write an Email
Source: Determiners and types of noun
2. Regular plurals Use a plural noun form after a number greater than one.
Correct Three students joined the tour.
Common trap · incorrect Three student joined the tour.
What goes wrong: the trap uses “student” where the correct sentence has “students”, so it no longer follows the rule.
Matters for: Complete the Words · Build a Sentence · Write an Email
Source: Nouns: form
3. Irregular plurals Some common nouns have plural forms that do not add a simple s.
Correct Two children joined the activity.
Common trap · incorrect Two childs joined the activity.
What goes wrong: the trap uses “childs” where the correct sentence has “children”, so it no longer follows the rule.
Matters for: Complete the Words · Build a Sentence · Write an Email
Source: Nouns: form
4. Noncount nouns Do not add a plural ending to noncount nouns such as information in standard academic use.
Correct We need more information.
Common trap · incorrect We need more informations.
What goes wrong: the trap uses “informations” where the correct sentence has “information”, so it no longer follows the rule.
Matters for: Complete the Words · Build a Sentence · Write an Email
Source: Information
5. A or an by sound Choose a or an by the next sound, not just the next written letter.
Correct The adviser gave us an hour.
Common trap · incorrect The adviser gave us a hour.
What goes wrong: the trap uses “a” where the correct sentence has “an”, so it no longer follows the rule.
Matters for: Complete the Words · Build a Sentence · Write an Email
Source: A/an and the
6. No a before a plural Do not put a or an directly before a plural count noun.
Correct They reserved two rooms.
Common trap · incorrect They reserved a two rooms.
What goes wrong: the trap adds “a”, so it no longer follows the rule.
Matters for: Complete the Words · Build a Sentence · Write an Email
Source: A/an and the
7. The for an identified item Use the when the following words identify a particular item for the reader.
Correct Please return the notebook I lent you.
Common trap · incorrect Please return notebook I lent you.
What goes wrong: the trap leaves out “the”, so it no longer follows the rule.
Matters for: Complete the Words · Build a Sentence · Write an Email
Source: A/an and the
8. Many with count plurals Use many with plural count nouns; use much with noncount amounts.
Correct We received many responses.
Common trap · incorrect We received much responses.
What goes wrong: the trap uses “much” where the correct sentence has “many”, so it no longer follows the rule.
Matters for: Complete the Words · Build a Sentence · Write an Email
Source: Much, many, a lot of, lots of: quantifiers
9. Possessive apostrophe Use apostrophe-s to show possession or a close relationship with a singular person or thing.
Correct The student's bag is under the desk.
Common trap · incorrect The students bag is under the desk.
What goes wrong: the trap uses “students” where the correct sentence has “student's”, so it no longer follows the rule.
Matters for: Complete the Words · Build a Sentence · Write an Email
Source: Possession
10. This and these Use this with a singular noun and these with a plural noun.
Correct These results are clear.
Common trap · incorrect This results are clear.
What goes wrong: the trap uses “This” where the correct sentence has “These”, so it no longer follows the rule.
Matters for: Complete the Words · Build a Sentence · Write an Email
Source: Determiners and types of noun
Previous ← Sentence foundations Next Basic verb forms → Other grammar topics
Frequently Asked Questions Which TOEFL tasks test nouns and determiners? + No task names grammar topics, but these rules matter most in Complete the Words, Build a Sentence, Write an Email. 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.