6 GMAT Grammar Rules You Must Know


You may have heard rumors that you need to know a lot of grammar for the GMAT. Unfortunately, it’s true that you’ll see GMAT grammar questions; however, the test focuses on just a few main concepts you need to know.

In this article, I’ll go over the six most important GMAT grammar rules, as well as offer tips for how to learn them so you can ace the sentence correction questions on test day.


Overview: GMAT Grammar

Grammar is tested on the GMAT primarily in sentence correction questions, which make up about a third of the verbal section (36 questions in total).

In sentence correction questions, you will be shown a sentence with an underlined portion, and five answer choices that give options for how to replace the underlined portion. The first answer choice is always exactly the same as the underlined portion of the sentence.

Sentence correction questions on the GMAT will ask you to select the answer choice that will make the sentence 1) grammatically correct, 2) concise, and 3) logical. Most questions will test you on more than one of these factors at a time.

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Keep in mind as you prepare for this section of the GMAT that GMAT grammar is based on specific rules. Even if a sentence would sound correct in normal daily conversation or writing, it might not be correct by GMAT standards, so it’s important to learn each of the grammar rules tested by the exam.

The good news is that GMAT grammar rules are also repetitive: as you practice, you’ll see the same rules being tested over and over again, which means that if you prepare well and thoroughly, you’ll know exactly what to expect on sentence correction questions.


Grammar is tested primarily on sentence corrections questions on the GMAT.
Grammar is tested primarily on sentence corrections questions on the GMAT.


6 Key GMAT Sentence Correction Rules

Let’s go over six of the most common GMAT grammar rules, alongside examples (authored by the Graduate Management Admissions Council, GMAC, which also writes the GMAT itself) from the GMATPrep Software.


#1: Dangling Modifiers

The GMAT loves to test you on modifiers, which are clauses, words, or phrases that describe other parts of a sentence. In the sentence, “My sister, the psychologist, is coming to visit,” for example, “the psychologist” modifies “my sister,” which is the subject of the sentence.

Dangling modifiers are the most common modifier-related errors on the GMAT. In a dangling modifier, the modifying phrase is misplaced, describing the incorrect word or phrase so that the sentence is illogical. Take a look at the following sentence and see if you can tell why it’s illogical.

A beautiful red-haired mermaid, the president thought Ariel was highly intelligent.

This sentence contains a dangling modifier: The president is likely not a beautiful red-haired mermaid (though that would be cool). The modifier “A beautiful red-haired mermaid” belongs next to the noun it modifies, which is Ariel. Let’s rewrite it to remove the dangling modifier:

The president thought Ariel, a beautiful red-haired mermaid, was highly intelligent.

Now let’s take a look at an official GMAT example.

dangling modifier 2

To spot dangling modifiers, look for introductory phrases followed by a comma. In this question, “architects and stonemasons” is the modifying phrase in question. The phrase needs to modify a noun, and one that is logical in the context of the sentence.

In answer choices B, D, and E, the modifying phrase is not following by a noun or noun phrase (answer choice E begins with a verb, ‘were,’ for example), so you can eliminate them.

In answer choice A, the phrase “architects and stonemasons” is modifying “huge palace and temple clusters.” It’s not logical for the palace and temple clusters to be architects and stonemasons, so you can eliminate this answer choice.

In answer choice C, “architects and stonemasons” is modifying “the Maya,” which makes sense in the context of the sentence. This is the correct answer.


#2: Proper Verb Tense

GMAT sentence correction questions often test students on proper verb tense usage. Remember that verb tenses (the basic ones are past, present, and future) give us information about when an action took place (or will take place, etc.). Verb tenses are generally supposed to remain consistent, unless there is a specific reason for the tense to shift within a sentence. For example:

By the time the police arrived, the robbers had fled.

Note the clue that the verb tense is supposed to change (in this case from past tense to past perfect): “By the time” lets us know that there was a sequence of events. In this sentence, the robbers fled before the police arrived, so that shift in time needs to be reflect by a shift in verb tense.

In the GMAT example below, the conditional construction of “if x happens, y will happen” requires the first half of the sentence to be in present tense and the second half of the sentence to be in the future tense. So we can immediately eliminate answer choices A and B.

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verb tense shifts

Answer choices C and D are less concise and precise than answer choice E because of the extraneous clauses they include (‘as they already did’) and (‘as they have already’), making answer choice E the correct option.


#3: Illogical Comparison

In the sentence “Mark loves chips more than his mom,” what’s wrong?

Well, unless Mark really loves chips, it’s unlikely to be true. What the writer is probably trying to say is “Mark loves chips more than his mom does.” The original sentence is an example of an illogical comparison.

Illogical comparisons compare apples to oranges, meaning that the things being compared either don’t make sense in context or don’t match up with each other grammatically (nouns being compared to verbs, for example).

Clues of an illogical comparison question on the GMAT include phrasing like “more/less than,” “like/unlike,” and “as…as.”

In this example, you’re being asked to compare “a typical automobile loan” to something else (the word “unlike” clues you into this). So you need to look for 1) a noun, since “ban” is also a noun, and 2) a noun that’s logical in the sentence’s context.

illogical comparison 5

Answer choices B and D can’t be correct, then, because they compare the “automobile loan” (a noun) to prepositions (“with” and “for”).

Answer choices A and C are incorrect because, while they start with nouns (“lease-loan buyer(s)”), they are illogical; a lease-loan buyer can’t be compared to a loan itself.

Answer choice E is correct. It compares “a typical automobile loan” to “a lease-loan.”  


Illogical comparisons can be spotted using clue words like "like" and "unlike."
Illogical comparisons can be spotted using clue words like “like” and “unlike.”



#4: Pronoun Usage

GMAT sentence correction questions test you on proper pronoun usage. Correct pronouns match their antecedent (the word they stand in for). For example, in the sentence, “Sara took off her hat,” “Sara” is the antecedent for “her.” Plural pronouns (we, they, them, us) match with plural antecedents, and singular pronouns (I, he, she, her, him, it) match with singular antecedents.

Let’s look at one example of incorrect pronoun usage. What’s wrong with this sentence?

I never go to that restaurant because they have moldy cheese.

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Who has moldy cheese? We can’t tell from the sentence. “They” is a plural pronoun, and its possible antecedents (“I” and “restaurant”) are both singular. We would rewrite it like this:

I never go to that restaurant because it has moldy cheese.

Now let’s take a look at a GMAT example of incorrect pronoun usage.

pronoun usage 2

In this example, the antecedent of “it” is “crab.” “They” and “their” (both plural pronouns) are incorrect pronouns because they don’t match with their antecedent (singular), so you can eliminate answer choices B and E. Answer choices A and D have no pronoun, so they are illogical (“because of living at great depths”—who/what is living at great depths?).

Answer choice C includes the correct, singular pronoun (“it”) and the appropriate verb (“lives”), so it’s the right option. Notice that it is also more concise than answer choices A and B, which is often a clue that an answer choice is a good one.


#5: Subject-Verb Agreement

GMAT sentence correction questions often include subject-verb agreement errors. The subject of a sentence must match with its verb; a singular subject has to accompany a singular verb, and a plural subject has to accompany a verb in the plural form.

A common trap you’ll see in subject-verb agreement questions is a prepositional phrase (a phrase that starts with a preposition and ends with a noun) that is wedged between the subject and the verb to confuse you.

Let’s look at an example of the “distracting extra phrase” trap:

This box of decorations belong upstairs.

The prepositional phrase in this sentence is “of decorations,” which you should ignore when figuring out the correct verb form to accompany the subject. “Box” is the subject, and it’s singular, so the verb form should be too; the singular present tense form of the verb “to belong” is “belongs,” not “belong,” so the sentence should read, “This box of decorations belongs upstairs.”

Now let’s go through a GMAT example of a subject-verb agreement error.

subject verb agreement 2

The subject you’re dealing with in this example is “cost” or “costs.” Its verb is “are” (before “prohibitive”), which is plural, so the subject has to be plural as well. This allows you to eliminate choices A and D right off the bat.

We’ll go over how to select the correct answer choice for this question in the next example.


#6: Idioms

An idiom, or idiomatic expression, is a common phrase in English, often involving prepositions. For example, one graduates “from” college, not “of” college. One “belongs to a club,” not “belongs with a club.”

GMAT sentence correction questions generally test more than one grammar error at once, and you’ll often see wrong answer choices that fix the original error but contain an incorrect idiom. Correct answer choices will always be grammatically and idiomatically sound.

Let’s look at an example:


When two choices are being compared, “whether” is the idiomatically proper choice rather than “if.” That means that answer choices A and D can be eliminated immediately based on their incorrect use of “if.”

“Being” is redundant (and unnecessarily wordy) when used after “undergoing,” because “undergoing” already lets you know that the conversion is in process, so answer choices B and C can be eliminated as well.

Answer choice E is correct based on idiom usage, a lack of redundancy, and concision.


3 Tips for Learning GMAT Grammar Rules

There are a few key ways to target GMAT grammar to prep for the sentence correction questions. Let’s go over the three top tips for mastering the exam’s grammar questions, undertaking effective GMAT grammar practice, and learning GMAT sentence correction rules.


#1: Use Flashcards to Study Idioms

It’s important to learn about the most common idioms you’ll encounter on the test as part of your GMAT grammar practice routine so you can eliminate answer choices that use idioms incorrectly right away. Once you get familiar with them, answer options with incorrect idiomatic expressions speed up the process of elimination.

Particularly if you’re a non-native English speaker, learning idioms can be a tricky aspect of your GMAT grammar prep. Creating and studying with flashcards that include the meanings of idioms as well as examples of their proper usage can help you get comfortable with GMAT idioms. Check out our guide to GMAT idioms to familiarize yourself with the most common ones.


#2: Review the Underlying Grammar Concepts

Your GMAT grammar practice should include a review of the basics of grammar, including parts of speech, sentence structure, modifiers, verb tense, and pronoun usage. Princeton Review’s Grammar Smart includes an overview of many of the GMAT-relevant grammar rules, as well as drills to complete as part of your prep. I would recommend Grammar Smart as your primary GMAT grammar book over generic grammar guides because they aren’t likely to be specifically relevant to the GMAT.


#3: Learn How Grammar Rules Are Tested on the GMAT

When you practice with the GMATPrep Software or other study resources, target GMAT grammar rules by selecting sentence correction practice questions. As you learn to identify various question types, you’ll become more aware with the way each of the GMAT sentence correction rules are tested on the exam. This will help you learn how to approach each grammar concept as it is presented on the GMAT and how to work through each question type more efficiently, effectively, and accurately.


Regular practice is key to learning the GMAT grammar rules.
Regular practice is key to learning the GMAT grammar rules.


What’s Next?

For more information about the verbal section as a whole, check out our article on mastering all three GMAT verbal question types.

Our guide to the best GMAT verbal practice materials will help you prepare for the verbal section of the exam more effectively.

Trying to understand each of the GMAT sections in more depth? Our comprehensive overview of all four sections of the test will help you out.

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Author: Laura Dorwart

Laura Dorwart is a Ph.D. student at UC San Diego. She has taught and tutored hundreds of students in standardized testing, literature, and writing.