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GMAT Sentence Correction: Semicolons & Commas

As a general rule, punctuation isn’t a point of English grammar that’s often explicitly tested on GMAT Sentence Correction questions. That said, there are two articles of punctuation that you should know some general usage rules about: semicolons and commas.

Occasionally, incorrect semicolon or comma usage will in fact be a reason for an error in a GMAT sentence correction question (see example below). Additionally, it’s important that you use punctuation correctly when writing your Analysis of an Argument essay as well. So, without further ado, let’s take a closer look.

Semicolons

A semicolon is a punctuation mark that is used to indicate a pause in a sentence, specifically one that is more pronounced than that indicated by a comma. There are two reasons for using a semicolon:

1) To separate independent clauses.

Remember that an independent clause can stand alone as a complete sentence; it contains a subject and a verb. Thus, when evaluating whether a semicolon or comma should be used to separate two connected thoughts in a sentence, simply check to see whether or not there’s a subject and verb on each side of the punctuation mark. For example:

“I ate day-old sushi for breakfast; I spent a week in the hospital.”

A semicolon is correctly used to designate the pause in the sentence because both sides are independent clauses.

2) To separate items that contain commas in a list.

In this case, to avoid having an overwhelming number of commas in the sentence, semicolons are used as a larger division of structure. An example of this would be when you’re listing several cities and states in the same sentence. For example:

“The students in the class hailed from several different locations, including Atlanta, Georgia; Chicago, Illinois; and Sacramento, California.”

Commas

Commas are used for pretty much everything else!

Specifically, a comma is a punctuation mark used to indicate a pause in a sentence, but one that is less pronounced than what would necessitate using a semicolon. Commas are also used to separate items in a list and to mark the place of thousands in a large numeral.

The key thing to remember with commas is that you cannot connect two independent clauses with just a comma. For example:

INCORRECT: The original inventor of the steam engine was James Watt, he was born in Scotland in 1736.

CORRECT: The original inventor of the steam engine was James Watt, born in Scotland in 1736.

Semicolons and Commas on the GMAT

With all of this in mind, try your hand at this example from the GMAT Review Official Guide, 13th ed. (p.693, #113):

As a baby emerges from the darkness of the womb with a rudimentary sense of vision, it would be rated about 20/500, or legally blind if it were an adult with such vision.

(A) As a baby emerges from the darkness of the womb with a rudimentary sense of vision, it would be rated about 20/500, or legally blind if it were an adult with such vision.
(B) A baby emerges from the darkness of the womb with a rudimentary sense of vision that would be rated about 20/500, or legally blind as an adult.
(C) As a baby emerges from the darkness of the womb, its rudimentary sense of vision would be rated about 20/500; qualifying it to be legally blind if an adult.
(D) A baby emerges from the darkness of the womb with a rudimentary sense of vision that would be rated about 20/500; an adult with such vision would be deemed legally blind.
(E) As a baby emerges from the darkness of the womb, its rudimentary sense of vision, which would deemed legally blind for an adult, would be rated about 20/500.

You should recognize that the original sentence is faulty because it fails to convey its meaning due to faulty construction. The sentence begins with a subordinate clause, whose subject is a baby; the subject of the main clause, it, appears to refer back to baby. However, it’s clear that it is intended to refer to the sense of vision the first time it is used and to the baby the second time. Thus, the whole sentence must be revised.

You can immediately eliminate answer choice A.

Answer choice B is incorrect because the final phrase is awkwardly and ambiguously attached to the sentence.

You should recognize that answer choice C is incorrect based on the rules described above! The phrase after the semicolon, qualifying it to be legally blind if an adult, isn’t an independent clause. Thus, the semicolon is improperly used.

Answer choice D is correct because the semicolon separates two independent clauses. One independent clause describes a baby’s vision, the other an adult’s.

Answer choice E is incorrect because the subordinate clause beginning with which is awkward and ambiguous.

Study these rules, make sure you’re clear on the difference between a semicolon and a comma, be sure to apply them correctly when writing your essay as well as when evaluating GMAT sentence corrections, and go out and dominate the GMAT!