GMAT SC Grammar: Phrases, Clauses, and Sentence Structure

In a sense, structure is everything in GMAT SC. If the structure is wrong-- either in terms of word form, word choice, or missing words-- the answer choice is wrong.

It's not that hard to spot structure errors in shorter sentences. Indeed, in a short sentence, you may recognize errors very swiftly, perhaps even instinctively.

But "swift and instinctive" isn't the approach you want to take with GMAT SC. There, you want to take a little more time to really look at the "deep structure" of long, complicated sentences. You want to be grammar conscious, rather than just reacting to grammar.

To do this, you need to be aware of the kinds of phrases, clauses, and other structures that act as the building blocks of sentences. Below, we'll review those structures.

Review of Phrases

There are three types of phrases you should pay close attention to in GMAT SC: noun phrases, verb phrases, and prepositional phrases. As you look at the definition of these phrases below, remember that "phrase," in grammar terminology, can mean a single word. A noun phrase can be just one noun, or a noun plus other words that modify it. And a verb phrase or prepositional phrase can also be one word long or contain multiple words. Also remember that one smaller phrase can be contained inside another. A verb phrase can contain a smaller prepositional phrase, a prepositional phrase can contain a noun phrase, and so on.

Types of phrases

  • Noun phrase: A noun, plus any other structures (such as determiners, adjectives, or prepositional phrases) that modify the noun.
    • Examples: 
      the dog
      the big dog
      the big dog in the house
  • Verb phrase: A verb, plus any other structures that modify the verb
    • Examples: 
      constantly runs
      constantly runs with great speed
  • Prepositional phrase: a preposition, plus any words that modify the preposition
    • Examples: 
      in the kitchen
      in light of the fact that she needs exercise

These three phrase types can be combined in different ways to form sentences. Here are a few example sentences made from the examples above:

  • The big dog constantly runs, in light of the fact that she needs exercise.
  • The dog runs in the kitchen.
  • The dog runs.
  • The big dog in the house constantly runs.

Some of these example phrases have other smaller phrases inside them. "The big dog in the house" is a noun phrase that contains the smaller prepositional phrase "in the house." In turn, "in the house" contains the verb phrase "the house" as its prepositional object. Look at the other example phrases above. How many times can you find a phrase-within-a-phrase in the examples?

Diagramming phrases
Often, GMAT SC will "hide" a mistake inside a small phrase within-a-phrase. So when one phrase contains other phrases, you need to be able to notice this. Check for problems in both the bigger phrase and the smaller "contained" phrases. To practice this skill, you can diagram phrases, identifying and labeling their elements.

Here is a "plain text" diagram of the phrase "the man on the hill":

[[the man] (<smaller noun phrase/main noun) [[on [the hill]]](<noun phrase/object of prepositional phrase)](<prepositional phrase that modifies main noun)](<entire noun phrase)

That's a very detailed diagram, of course. If you're confident that you understand the finder details of the connection between phrases, you don't necessarily have to write them all down. Instead, you could make a simpler diagram such as:

[[[the man (<main noun) [[on [the hill](<noun phrase)](<prepositional phrase)](<entire noun phrase)

That said, use as much detail as you need in order to study effectively and understand the structures within a phrase.

The diagrams above use brackets, parenthesis, and italics to label the parts of the phrase. You can also visually diagram a phrase by using pen and paper or a whiteboard computer program (such as MS Paint). Here's a more visual diagram of "the man on the hill":



Many incorrect SC answers involve phrases that are incomplete, unclear, or improperly formed. So the information and practice activities we've just gone over are very important on the GMAT.

Phrases in GMAT SC sentences
Now, let's look at what phrase structure looks like in a typical GMAT SC sentence. Here is an example sentence from Magoosh GMAT practice: 

  • Original sentence:
    China perennially has been the world's leader in tea production, and its fascination with tea has deep historical roots, as exemplified by the tea ceremony, which has analogs in Japan and Korea.
  • That same sentence, with phrases diagrammed:


Follow-up practice

Try diagramming the phrases in a few GMAT sentences of your own. You could use highlighting and bullet points as seen above. Or you could do a more visual diagram of the sentence, using pen and paper or a whiteboard, as seen in the earlier diagram of the phrase "the man on the hill."


Review of Subjects, Predicates, Sentences and Clauses

You (probably) don't use grammar terminology in everyday conversation. So let's start start with a quick review of the key grammar terms at hand.

  • subject: the main noun phrase in a clause or sentence
  • predicate: the main verb phrase in a sentence or clause; modifies the subject of a clause or sentence
  • clause: any grammar structure that contains a subject and predicate
  • sentence: a complete, self-contained statement, marked in writing by a capital letter at the beginning, and either a period, exclamation point, or question mark at the end. (In GMAT SC, the punctuation at the end of a sentence will nearly always be a period.)

The relationship between subjects, predicates, clauses, and sentences

  • Both a clause and sentence have a subject and predicate. (Sentences with more than one clause will contain more than one subject and predicate.)
    • Ex: The dog chased the cat. (“The dog” is the subject; "chased the cat” is the predicate; "The dog chased the cat." is both a clause and a complete sentence.)

  • A predicate can take many forms, such as:
    • Verb only: The dog ate. (The predicate is most likely to be verb-only when the verb or verb phrase is intransitive.)
    • Verb and direct object: The dog ate the meat.
    • Verb and prepositional phrase: The dog ate from a plate.
    • Verb and adjective: The dog is big.
    • Verb and direct object and prepositional phrase: The dog ate the meat from the plate.
    • And so on….

In GMAT SC, wrong answers will often feature a mistake between the subject and predicate. For instance, the subject could be missing, or a verb could be missing from the predicate. Or there could be a contradiction between the subject and predicate, such as a singular noun in the subject but a plural verb in the predicate. There are other possibilities too, so be aware of subjects and predicates and be ready to check them with care on the GMAT.

The difference between a sentence and a clause

As I mentioned earlier, a sentence is “marked” as complete and self-contained, because it begins with a capital letter and ends with final punctuation.

On the other hand, as I said, a clause is any string of words that has both a subject and a predicate. A complete sentence can be a clause. However, other clauses are just part of a larger sentence. 

The two types of clauses

There are two types of clauses: independent clauses and dependent clauses

Independent clauses could form their own sentence if they were written with a capital letter at the beginning and punctuation at the end. A complete sentence is an independent clause, but many other complete sentences consist of independent clauses with other phrases or clauses attached to them. 

  • Ex: It’s raining outside.
    (In this case, the
    independent clause is the entire sentence.)
  • Ex: It’s raining outside, which is unfortunate.
    (Here, the
    independent clause is the opening part of the sentence, and it is followed by a dependent clause.)
  • Ex: It’s raining outside, and I forgot my umbrella.
    (In this case, two
    independent clauses are joined by the conjunction “and.”)
  • Ex: At the moment, it's raining outside.
    (A prepositional phrase is attached to the front of the independent clause. This could also be re-worded as "It's raining outside at the moment.")

Dependent clauses, if isolated, don’t work as complete sentences. They can only be part of a larger sentence, and they add information to an independent clause.

  • Ex: Because she had a meeting after work, she got home late. (“Because” makes the dependent clause unable to stand on its own as a sentence. If you don’t add an independent clause, the reader is left to ask “Because what?”)
  • Ex: The music played until the CD player was unplugged. (Here, “until” places the clause inside a prepositional phrase. Any clause inside a prepositional phrase is dependent.)
  • Ex: It is important they be allowed to participate. (Here “they be allowed to participate” is a dependent clause, written in subjunctive mood.)

There are many different grammar forms that create dependent clauses. What’s important is to be able to recognize a dependent clause when you see it in a sentence, regardless of the reason the clause is dependent. Remember the real litmus test for a dependent clause: if you capitalized the clause and gave it end punctuation, would work as a complete sentence? If the answer is "no," then you have a dependent clause.

In SC on the GMAT, watch for dependent clauses that are wrongly being used as independent clauses. And watch for independent clauses that aren't properly marked, or have a missing subject or missing verb. And in general, be aware of where clauses begin and end, so you can properly analyze all structures in the sentence.

Follow-up practice

Quickly recognizing and analyzing clauses is an essential GMAT SC skill. You can build this skill by diagramming GMAT SC sentences to mark the clauses. Again, you can diagram these on a computer by using highlighting, bold type labels, bullet points etc. Or you can diagram such sentences with the pen/paper or whiteboard method. In some cases, you may want to reproduce and separately diagram a dependent clause. Below are some example SC sentences from Magoosh GMAT, diagrammed:



Applying Knowledge of Each Grammatical Feature to Real SC Questions

So far, we've looked at sentences, but not entire GMAT SC questions with multiple answer choices. But in this final part of the tutorial, we'll make the leap from grammar theory to grammar application. Below, we'll go through a full Magoosh GMAT SC question, answer choices and all. Step-by-step, I'll show you how to solve this SC problem using your knowledge of noun phrases, verb phrases, prepositional phrases, predicates, clauses, and sentences.

Example Question

An increase in the number of protons, when unaccompanied correspondingly by an increase in the number of neutrons, almost always produce an unstable isotope of an element higher on the Periodic Table.

  • A. when unaccompanied correspondingly by an increase in the number of neutrons, almost always produce
  • B. when not accompanied by a corresponding increase in the number of neutrons, almost always produce
  • C. when that is unaccompanied correspondingly by an increase in the number of neutrons, almost always produces
  • D. if not accompanied by a correspondingly increased number of neutrons, almost always produce
  • E. if not accompanied by a corresponding increase in the number of neutrons, almost always produces

Solving the Example Question with Grammar Principles

So how do we find the right answer, using grammar knowledge? Let’s start by applying all of this grammar knowledge to answer choice (A). Is (A) correct, based on proper use of noun phrases, verb phrases, subjects, predicates, and dependent/independent clauses?

  • Prepositional phrases: You should notice in (A) that “when… neutrons” is a prepositional phrase. This phrase is closed off by commas.

  • Clauses: The prepositional phrase “when… neutrons” stands in the middle of the of a clause in (A), which is: An increase in the number of protons almost always produce an unstable isotope of an element higher on the Periodic Table. A quick inspection shows that this clause is the only clause in the sentence, and it’s independent. So basic clause structure in (A) is OK.

  • Subjects and predicates: The GMAT loves to test improper or incomplete subject predicate pairings. So the next thing you should do is identify the subjects and predicates in the sentence’s independent clause. Here, the subject is “An increase in the number of protons.” The predicate is “almost always produce an….”
  • Noun phrases and verb phrases: Remember, subjects consist of noun phrases. Predicates consist of the verb phrase, plus anything that follows the verb phrase. The noun phrase of this sentence’s clause is again “An increase in the number of protons.” The main verb phrase in the predicate is “almost always produce,” with “almost” and “always” as adverbs, and “produce” as the verb. But wait a minute. In the noun phrase, the main noun is “an increase." (Since the other noun phrase, “the number of protons” is actually inside the subject’s modifying prepositional phrase.) “Increase” is a singular noun. “Produce” is a plural verb. This is an error! You can eliminate answer (A).

So, by applying knowledge of all grammar forms, you can identify and examine the subject and predicate of this GMAT SC sentence. You can recognize that “produce” modifies the subject, and modifies it incorrectly.

Based on your grammatical analysis of (A), you can also eliminate answers (B) and (D). These choices too have the verb “produce” incorrectly modifying the noun “increase.”

This leaves (C) and (E). Let’s look at those choices again, complete with the sentence that surrounds the answer choice. Then, let’s apply grammar knowledge once more to see which of these two are correct. Here's the prompt again, followed only by the answers we haven't eliminated yet:

An increase in the number of protons, when unaccompanied correspondingly by an increase in the number of neutrons, almost always produce an unstable isotope of an element higher on the Periodic Table. 

  • C) An increase in the number of protons, when that is unaccompanied correspondingly by an increase in the number of neutrons, almost always produces an unstable isotope of an element higher on the Periodic Table.
  • E) An increase in the number of protons, if not accompanied by a corresponding increase in the number of neutrons, almost always produces an unstable isotope of an element higher on the Periodic Table.

If you look at (C), you can see that the prepositional phrase has been changed so that it contains a full clause, beginning with “that is….” The word “that” serves as a demonstrative pronoun-subject. (You can see details on demonstratives in this Magoosh GMAT Blog post.) So in this clause, what’s the verb phrase? It’s “is unaccompanied correspondingly.” “Is unaccompanied” is the verb, and “correspondingly” is the adverb. But wait… in English, the normal position of the adverb is before the verb, not after it. So we have some awkwardness here. This may eliminate (C). But let’s apply grammar knowledge to (E) before we make up our minds.

In (E), we have an “if” clause instead of a prepositional phrase. At first, it seems like this clause is incomplete. There’s no subject. But remember, in if-clauses, the phrase “it is” can be contracted. This means the subject and verb “it is” can be left out but implied. So the subject and predicate are both there in the clause, but are contracted and implied. So the “if” clause has an acceptable structure here. Next, let’s look at the prepositional phrase inside the “if" clause, the one that starts with “by a….” Remember that in GMAT rules, only a noun phrase can be a prepositional object. We’re OK here in (E), because “increase” is a noun. The same goes for the smaller prepositional phrase within “by… neutrons.” This phrase, with the preposition “in” is has “number” for an object, and “number” is a noun. So (E) is correct!.

Follow-up activity 

Go through additional SC questions. Use your knowledge of prepositional phrases, verb phrases, and noun phrases to locate and examine the clauses, subjects, and predicates in each sentence. Then apply that knowledge and select the correct answer choice.


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