GMAT Sentence Correction (SC) is a vocabulary and grammar question type that many test-takers underestimate. The question format is straightforward — identify the error in the underlined portion and choose the best correction — but the rules tested span a wide range of grammar, style, and diction issues. This guide covers the most frequently tested rules and the vocabulary distinctions that regularly determine correct answers.
Note: GMAT Sentence Correction was removed from the GMAT Focus Edition (introduced in 2023). However, it remains a component of the Classic GMAT and is still tested by many institutions that use legacy score reports. The grammar and vocabulary knowledge in this guide also applies to GRE Text Completion, GMAT Reading Comprehension, and any standardized writing section.
The Top 10 Grammar Rules Tested in GMAT Sentence Correction
Rule 1: Subject-Verb Agreement
The verb must agree with its subject in number — even when long modifier phrases separate the subject from the verb. Common trap: collective nouns (team, staff, committee) are singular and take singular verbs in American English. "The committee has decided" (not "have").
Tricky cases: "Neither the CEO nor the managers were informed" (verb agrees with the nearer subject). "Each of the proposals was evaluated" (each = singular). "A number of issues have been raised" vs. "The number of issues has increased" (a number = plural; the number = singular).
Rule 2: Pronoun Reference
Pronouns must have clear, unambiguous antecedents. "The manager told his assistant that he needed to prepare the report" — unclear who "he" refers to. GMAT SC questions test whether the pronoun could refer to multiple nouns in the sentence. The correct answer eliminates the ambiguity.
Rule 3: Parallel Structure
Items in a list or pair must be grammatically parallel. "The plan requires increasing production, to reduce costs, and that quality is maintained" violates parallelism. Correct: "increasing production, reducing costs, and maintaining quality." Lists following FANBOYS conjunctions (for, and, nor, but, or, yet, so) and correlative conjunctions (both/and, either/or, not only/but also, neither/nor) must be perfectly parallel.
Rule 4: Modification
Modifying phrases must be as close as possible to the noun they modify. A misplaced modifier creates an illogical sentence. "Having studied for years, the exam was finally passed" — the modifier "having studied" should modify a person, not the exam. Correct: "Having studied for years, he finally passed the exam."
| Error Type | Example of Error | Corrected Version |
|---|---|---|
| Dangling modifier | Walking down the street, the trees were beautiful. | Walking down the street, she noticed the beautiful trees. |
| Misplaced modifier | She almost drove her children to school every day. | She drove her children to school almost every day. |
| Squinting modifier | Children who exercise often develop better habits. | Children who often exercise develop better habits. / Children who exercise develop better habits more often. |
| Split infinitive (style) | To boldly go where no one has gone | To go boldly where no one has gone (GMAT prefers unsplit) |
Rule 5: Verb Tense Consistency
Verb tenses must be logically consistent within a sentence. The simple past establishes a time frame; events that occurred before that time require the past perfect ("had done"). "After the committee reviewed the proposal, the director approved it" (both past — simultaneous). "After the committee had reviewed the proposal, the director approved it" (past perfect — review occurred first).
Rule 6: Idiom and Preposition Usage
English idioms pair specific verbs with specific prepositions. GMAT tests these pairings directly. Common tested idioms:
- Attribute X to Y (not "attribute X with Y")
- Distinguish X from Y (not "distinguish X and Y")
- Compare X with Y (comparing to = making an analogy; comparing with = examining similarities and differences)
- Responsible for (not "responsible to do")
- Result in (not "result to")
- Regard as (not "regard to be")
Vocabulary Distinctions That Determine Correct Answers
Several GMAT SC questions turn on vocabulary distinctions — choosing between two grammatically correct options based on precision of word choice.
| Pair | Correct Use | Common Error |
|---|---|---|
| Affect / Effect | Affect (verb): to influence. Effect (noun): the result. Effect (verb, rare): to bring about. | "The decision effected team morale" should be "affected." |
| Less / Fewer | Fewer = countable nouns. Less = uncountable nouns. | "Less workers" should be "fewer workers." |
| That / Which | That introduces restrictive clauses (no comma). Which introduces non-restrictive clauses (comma before which). | "The report which was submitted late..." (if the clause is restrictive, use "that"). |
| Between / Among | Between: two things. Among: three or more. | "The funds were divided between the three departments" should use "among." |
| Like / As | Like: used before nouns/pronouns. As: used before clauses (subject + verb). | "Like I said" should be "as I said" (because a clause follows). |
| Due to / Because of | Due to: modifies nouns. Because of: introduces adverbial phrases modifying verbs. | "The delay was due to weather" ✓. "We were delayed due to weather" should use "because of." |
Rule 7: Comparisons Must Be Logical and Parallel
GMAT strongly tests comparison construction. You can only compare like things. "The profits of Company A are higher than Company B" is wrong — you're comparing profits to a company. Correct: "The profits of Company A are higher than those of Company B."
Rule 8: Countability
Quantifiers must match noun countability. Many/few/fewer apply to countable nouns. Much/little/less apply to uncountable nouns. GMAT tests this with: number of (countable) vs. amount of (uncountable); fewer vs. less; many vs. much.
Rule 9: Concision and Redundancy
GMAT prefers concise construction. Redundant expressions to avoid: "the reason why... is because" (use "the reason... is that"), "more superior" (superior already means more), "refer back" (refer already means back), "advance planning" (planning is already in advance).
Rule 10: Active vs. Passive Voice
GMAT generally prefers active voice for concision and clarity. Passive voice is acceptable when the agent is unknown, unimportant, or when the object of the action is the topic of the sentence. Never switch from active to passive in a parallel construction.
The Most Important Conjunctions for SC
Conjunctions signal logical relationships — and the wrong conjunction produces an illogical sentence even when the grammar is otherwise correct. Although/despite signal contrast (with a concession). Because/since signal causation. While can mean "at the same time" or "whereas" — in GMAT SC, the distinction matters and can make an answer choice ambiguous.
For vocabulary supporting GMAT verbal more broadly, see our Critical Reasoning vocabulary guide and the 200 most-tested GMAT words.
FAQ
Is Sentence Correction still on the GMAT?
Sentence Correction was removed from the GMAT Focus Edition in 2023. The new format includes Data Insights, Quantitative Reasoning, and Verbal Reasoning (which now contains only Critical Reasoning and Reading Comprehension). However, test-takers using Classic GMAT scores, preparing for legacy requirements, or studying grammar for general verbal improvement will still benefit from this content.
What is the "that/which" rule in GMAT SC?
"That" introduces restrictive clauses — clauses that are essential to identifying which thing you mean. No comma precedes them. "Which" introduces non-restrictive clauses — clauses that add optional information. A comma precedes them. "The proposal that was submitted late was rejected" (restrictive — tells you which proposal). "The proposal, which was submitted late, was rejected" (non-restrictive — provides additional information about a proposal already identified).
How much of GMAT Sentence Correction is vocabulary vs. grammar?
Approximately 60–70% is grammar (subject-verb agreement, parallelism, modification, tense) and 30–40% is vocabulary/diction (word choice, idiom, like/as, that/which, affect/effect). Both components matter — a grammatically perfect sentence with a wrong word choice will still be wrong in GMAT SC.
What is the fastest way to improve Sentence Correction accuracy?
Learn the top 10 rules in this guide, then do 15–20 SC questions per day and analyze every error. For each wrong answer, identify which rule you violated. Within 2–3 weeks, you will have encountered every major error type multiple times. Pattern recognition — not rule recitation — is the key to speed and accuracy in GMAT SC.
Practice These Words With Visual Flashcards
PassGREGMAT's visual flashcard system uses real photos to lock vocabulary into long-term memory. Free to start — no account needed.