GMAT Sentence Correction Rules: The Foundational Grammar
Subject-Verb Agreement and Pronoun Agreement
At the core of verb agreement GMAT questions is the requirement that a verb must match its subject in number. The test makers often obscure the subject by inserting long prepositional phrases or additive phrases (such as "as well as," "in addition to," or "along with") between the subject and the verb. It is vital to remember that these additive phrases do not change the number of the subject. For instance, in the phrase "The CEO, along with her directors, is attending," the singular subject "CEO" dictates the singular verb "is."
Similarly, pronoun agreement requires that every pronoun refers clearly to a single, logical antecedent. A common trap involves the use of "it" or "they" when the antecedent is ambiguous or non-existent in the sentence. GMAT examiners frequently use collective nouns—such as "team," "committee," or "corporation"—which are treated as singular in American English. Therefore, a corporation must be referred to as "it" rather than "they." If a pronoun can logically refer to more than one noun in a sentence, the sentence suffers from pronoun ambiguity, a frequent reason for an answer choice to be discarded during the elimination process.
Verb Tense Consistency and Sequence
GMAT verbal grammar requires a sophisticated understanding of the sequence of events. While simple past and present tenses are common, the GMAT frequently tests the past perfect tense to clarify the order of two past actions. The formula for the past perfect is "had + past participle." This tense must be used to indicate the action that occurred furthest in the past. For example, "By the time the auditors arrived, the clerk had destroyed the evidence."
Another critical area is the use of the conditional mood and the subjunctive mood. The subjunctive is used to express wishes, proposals, or requirements, often following verbs like "suggest," "demand," or "insist." In these cases, the GMAT requires the base form of the verb: "The board recommended that the CEO resign" (not "resigns" or "should resign"). Understanding these sequence rules prevents you from choosing answers that incorrectly shift tenses, which would obscure the timeline of the narrative or the intent of the speaker.
The Role of Idioms and Diction
Idiomatic expressions are fixed phrases that do not necessarily follow a broader grammatical rule but are accepted as standard. In GMAT Sentence Correction, idioms are often the deciding factor between two otherwise grammatically correct options. Common examples include "distinguish between X and Y" (rather than "distinguish X from Y") or "consider X Y" (rather than "consider X to be Y").
Diction involves choosing the correct word for the context. The GMAT often tests pairs that are frequently confused in casual speech, such as "economic" (relating to the economy) versus "economical" (thrifty or cost-effective). Because there is no central logic to idioms, high-scoring candidates often maintain an idiom list during their preparation. However, the GMAT has shifted slightly away from obscure idioms in recent years, focusing more on logical predication. Nevertheless, the ability to recognize correct prepositional pairings remains a fundamental skill for navigating the verbal section's more difficult questions.
Parallelism: Creating Balanced and Logical Structures
Parallelism in Lists and Correlative Conjunctions
Parallelism GMAT rules dictate that elements serving the same function in a sentence must follow the same grammatical form. This is most visible in lists of three or more items. If the first two items are gerunds (verbs ending in -ing), the third must also be a gerund. For example, "The job involves filing, typing, and answering phones" is correct, whereas "The job involves filing, typing, and to answer phones" is a violation of parallel structure.
This rule extends to correlative conjunctions, which are pairs of words that join ideas. Common pairs include "either...or," "neither...nor," "not only...but also," and "both...and." The GMAT requires that the grammatical structure following the first part of the pair matches the structure following the second. If you have "not only by investing," you must follow it with "but also by saving." This symmetry ensures that the sentence is balanced and that the weight of each idea is distributed evenly, which is a hallmark of the high-quality writing the GMAT seeks to identify.
Parallelism in Comparisons (Like/Unlike, As/Than)
Comparisons are a specialized form of parallelism that the GMAT uses to test your logic. The primary rule is that you must compare like things. A common error involves comparing a person to a quality or a company to its products. For example, "Like the previous CEO, the new CEO’s strategy is aggressive" is incorrect because it compares a person (the previous CEO) to a strategy. The correct version would be "Like the previous CEO’s strategy, the new CEO’s strategy is aggressive."
Distinguishing between "like" and "as" is another frequent challenge. In GMAT grammar, "like" is used to compare nouns, while "as" is used to compare clauses (which include a verb). For example, "He works like a pro" is correct, but "He works as a pro does" is required if a verb follows. Furthermore, the word "than" is used in comparative structures involving adjectives (e.g., "more than," "faster than"). Ensuring that both sides of the "than" or "as" are grammatically and logically equivalent is essential for avoiding the "apples to oranges" comparison trap.
Identifying and Correcting Faulty Parallelism
Faulty parallelism often occurs when a sentence attempts to link a noun with a clause or an infinitive with a gerund. To identify these errors, candidates should use the Root Phrase method: isolate the part of the sentence that leads into the list and then read that root with each item individually. If the root does not flow logically into every item, the parallelism is broken.
Consider the sentence: "The consultant is responsible for analyzing the data, reporting to the board, and the implementation of new policies." Using the root "The consultant is responsible for..." we find that "analyzing" and "reporting" work, but "the implementation" (a noun phrase) does not match the preceding gerunds. Correcting this requires changing the final element to "implementing." On the GMAT, parallelism is often the "silver bullet" that allows you to eliminate three out of five answer choices quickly, as the test makers frequently use complex, multi-line structures to hide simple violations of symmetry.
Modifiers: Placement, Clarity, and Logic
Misplaced and Squinting Modifiers
Modifiers GMAT questions focus on the relationship between a descriptive phrase and the noun it modifies. The fundamental rule is that a modifier must be placed as close as possible to the noun it describes. A misplaced modifier occurs when the descriptive phrase is separated from its target, often leading to an unintended or nonsensical meaning. For example, "The waiter served a steak to the man that was overcooked" implies the man was overcooked, rather than the steak.
A squinting modifier is a more subtle error where a word (usually an adverb) is placed such that it could modify the word before it or the word after it. For instance, in the sentence "The board decided on Friday to vote," it is unclear whether the decision happened on Friday or the vote was scheduled for Friday. The GMAT prizes clarity and will always prefer an answer choice that moves the modifier to an unambiguous position. When reviewing answer choices, look for variations in the placement of adverbs like "only," "almost," and "even," as their position can significantly alter the sentence's logical meaning.
Dangling Modifiers and How to Fix Them
An introductory modifier that starts with a participle (an -ing or -ed word) must describe the subject of the main clause that follows the comma. A dangling modifier occurs when the subject being described is missing from the sentence or is not the subject of the following clause. For example: "Walking to the store, the rain started to fall." This sentence suggests that the rain was walking to the store.
To fix a dangling modifier, you must either change the subject of the main clause or turn the modifier into a full subordinate clause. The GMAT frequently uses the passive voice to create dangling modifiers (e.g., "Having finished the report, the computer was turned off"). Since the computer did not finish the report, this is an error. The correct version must introduce the person who finished the report: "Having finished the report, the analyst turned off the computer." Identifying the "doer" of the action in an introductory phrase is a reliable strategy for spotting these structural flaws.
Essential vs. Non-Essential Modifier Clauses
Distinguishing between restrictive (essential) and non-restrictive (non-essential) modifiers is crucial for both punctuation and meaning. In GMAT conventions, "that" is used for restrictive clauses which are necessary to identify the noun, while "which" is used for non-restrictive clauses that provide extra information. Non-restrictive clauses must be set off by commas. For example, "The cars that have faulty brakes should be recalled" (only specific cars) versus "The cars, which have faulty brakes, should be recalled" (all the cars in question have faulty brakes).
Errors often arise when a "which" clause is used without a comma or when it is used to modify an entire preceding clause rather than the noun immediately before it. The GMAT generally forbids the use of "which" to refer to a whole idea; instead, it requires a more precise structure, such as using a participle or a summary noun (e.g., "...a development that..."). Understanding the specific constraints of relative pronouns allows you to navigate complex sentences where multiple modifiers are layered upon one another.
Concision, Clarity, and Effective Expression
Eliminating Redundancy and Wordiness
One of the most important sentence correction strategies is the principle of concision. If two answer choices are both grammatically correct and convey the same meaning, the shorter, more direct version is almost always the correct one. The GMAT penalizes redundancy, which is the use of words that repeat the same meaning. Common GMAT redundancies include "sum total," "period of time," "reason why," and "collaborate together."
Wordiness differs from redundancy in that it involves using a long, convoluted phrase where a single word or a simpler structure would suffice. For example, using "the fact that" is often a sign of wordiness. Instead of saying "Despite the fact that he was tired," a more concise version would be "Although he was tired." However, candidates must be careful: concision is a secondary priority to grammatical correctness and logical clarity. Never choose a shorter answer if it introduces a grammar error or changes the intended meaning of the original sentence.
Avoiding Ambiguity and Vagueness
Clarity is a non-negotiable requirement in GMAT Sentence Correction. Ambiguity often stems from poor pronoun reference or weak transitions. A sentence is vague if the relationship between its parts is not explicitly defined. For example, the use of "this" or "that" as a standalone subject pronoun is often considered too vague on the GMAT. Instead of saying "This led to a decline in sales," the GMAT prefers "This trend led to a decline in sales."
Another source of ambiguity is the improper use of comparative adjectives. When comparing two things, use the comparative form (e.g., "stronger," "more efficient"). When comparing three or more, use the superlative form (e.g., "strongest," "most efficient"). Using a superlative for only two items is a logical error. By ensuring that every word has a specific, unambiguous role in the sentence, you align your choices with the GMAT’s standard for professional-grade business communication.
The GMAT's Preference for Active Voice
While the passive voice is not grammatically incorrect, the GMAT strongly prefers the active voice because it is more direct and concise. In the active voice, the subject performs the action: "The manager wrote the report." In the passive voice, the subject receives the action: "The report was written by the manager." The passive voice often requires more words and can obscure who is responsible for an action.
However, there are instances where the passive voice is the correct choice, particularly if the performer of the action is unknown or if the focus should be on the recipient. You should not automatically eliminate the passive voice, but if you are stuck between an active and a passive construction that are otherwise equal, the active one is likely the intended answer. This preference is part of the GMAT's broader goal of testing your ability to communicate efficiently in a corporate environment where brevity and accountability are valued.
The Decision-Making Process for Sentence Correction
A Step-by-Step Error Identification Method
To master Sentence Correction, you must move away from reading the whole sentence and "feeling" the error. Instead, adopt a systematic process. First, read the original sentence carefully to identify the core Subject-Verb-Object structure. This helps you ignore fluff and focus on the skeleton of the sentence where most errors occur. Next, look for "markers" that signal specific error types: a comma followed by "and" signals parallelism; the word "which" signals a modifier; a pronoun like "it" signals an agreement issue.
Once an error is identified in the original sentence (Choice A), eliminate it and any other answer choices that repeat that same error. This process of vertical scanning—comparing the answer choices against each other rather than reading them in isolation—allows you to spot the differences in construction. By focusing only on the differences, you avoid the fatigue of re-reading parts of the sentence that are identical across all choices.
Comparing Answer Choices Systematically
After eliminating choices based on definitive grammar rules, you may be left with two or three options. At this stage, compare the remaining choices to see how they differ. One might use a different verb tense, while another might change the placement of a modifier. Evaluate these differences based on logical predication: which version makes the most sense?
Exam Rule: If an answer choice changes the meaning of the original sentence to something nonsensical or illogical, it is incorrect, even if it is grammatically perfect.
For example, if the original sentence implies a causal relationship and an answer choice turns it into a mere sequence of events, the original meaning (if logical) should be preserved. This systematic comparison ensures that you are not just looking for "correctness" in a vacuum, but the best expression of the intended idea.
Common Trap Answers and How to Avoid Them
Expert GMAT test-takers are aware of common traps designed to lead candidates to the wrong choice. One such trap is the "Sounds Good" choice—an option that uses sophisticated vocabulary but contains a subtle structural flaw like a misplaced modifier. Another is the "Fixes the Original Error" trap, where an answer choice corrects the problem found in Choice A but introduces a new, different error later in the sentence.
To avoid these, always read the entire chosen answer back into the context of the full sentence. Never assume that because the first half of an answer choice is correct, the second half is also sound. The GMAT often hides the real error at the very end of a long, complex sentence. By maintaining a skeptical mindset and verifying every part of the structure, you can avoid these common pitfalls and maintain a high level of accuracy.
Advanced Topics: Quantity Words and Logical Predication
Rules for 'Number' vs. 'Amount,' 'Fewer' vs. 'Less'
Precision in quantity is a frequently tested aspect of GMAT grammar rules. The GMAT distinguishes between countable and uncountable nouns. For countable nouns (items you can count individually, like "dollars," "employees," or "books"), you must use "number," "fewer," and "many." For uncountable nouns (bulk quantities like "money," "staff," or "water"), you must use "amount," "less," and "much."
A common error is saying "less than 50 people," which is incorrect because people are countable; the correct form is "fewer than 50 people." Similarly, "the amount of emails" should be "the number of emails." These distinctions are often used in the middle of complex sentences to see if the candidate can maintain grammatical precision under the pressure of time. Mastering these pairs allows for quick eliminations in questions that might otherwise seem confusing.
Ensuring Logical Meaning After Correction
Logical predication refers to the requirement that the parts of a sentence must logically make sense together. A sentence can be grammatically perfect but logically flawed. For example, "The growth of the company was fast, unlike its competitor." Grammatically, this is fine, but logically it is flawed because you are comparing "growth" (a quality) to a "competitor" (an entity).
To ensure logical predication, ask yourself: "Who is doing what?" and "Does this description actually apply to this noun?" GMAT questions often involve complex business scenarios where the relationship between data points or corporate actions must be clear. If a sentence suggests that a "price" increased "itself," it is logically inferior to a sentence stating that a "company" increased its "price." Logic is the final arbiter in Sentence Correction.
Stylistic Preferences vs. Grammatical Rules
In the highest difficulty levels of the GMAT, you may encounter questions where multiple choices are grammatically correct. Here, the test evaluates stylistic preferences. Beyond the preference for the active voice and concision, the GMAT also favors parallelism of thought. This means that if a sentence starts by discussing a trend, it should continue to focus on that trend rather than abruptly shifting focus to a different subject.
Another stylistic preference is the use of the subjunctive mood for hypothetical situations. While modern speech often uses "was" in hypothetical "if" clauses (e.g., "If I was you"), the GMAT strictly requires "were" (e.g., "If I were you"). These nuances distinguish the top 10% of test-takers. By treating Sentence Correction as a test of logic and formal style rather than just a grammar quiz, you can approach the Verbal section with the precision and authority required for a top GMAT score.