Correct Comma Usage on the GMAT

by on July 26th, 2015

GMAT-blog-comma-usageThe humble comma is often one of the trickiest punctuation marks for students. Of all levels to understand, especially when preceding the word “and.” Although it would appear to be straightforward when (and when not to) use a comma, there are two specific circumstances you should be aware of when tackling both the Sentence Correction and AWA sections of the GMAT. Not only will your knowledge of these circumstances help you avoid incorrect answer choices on Sentence Correction questions, displaying a mastery of commas will further enhance your authority when making arguments throughout your AWA essay.

We’ll walk you through two situations in which you should (and should not) use a comma after “and” on the GMAT, as well as in your everyday communication with friends and colleagues alike.

1. Comma usage when combining three or more items

For grammar nerds, the serial comma (sometimes referred to as the Oxford comma) is one of the more divisive punctuation marks known to man. In the simplest terms, a serial comma is placed just before a coordinating conjunction (and, or, not) in a series of three or more items. While the debate rages on amongst writers everywhere, the serial comma is important to understand for the following reasons: it adds clarity and prevents confusion. Consider the following sentence, which we’ve written with and without a serial comma.

My mother asked me to select a snare drum from a collection made of maple, birch, poplar and cedar and mahogany.

My mother asked me to select a snare drum from a collection made of maple, birch, poplar and cedar, and mahogany.

While neither sentence is grammatically incorrect, the first example is unclear. Without the serial comma, we can’t be sure if one snare drum is made from a combination of any of the final three woods, or if each wood represents a unique snare drum. However, the second example is more specific, tipping off the reader to the fact that one snare drum is made of a combination of only poplar and cedar. The serial comma will be particularly useful when writing a response in the AWA section of the GMAT. You’ve been training to be as clear as possible in your writing, and when dealing with a series of items, knowing when to use a serial comma will set your essay apart from the pack.

Bonus fact: Many news publications (including The Economist) do not use the serial comma. This decision is rooted not in disdain for clarifying commas, rather in an editorial strategy that seeks to save as much space as possible, even the space taken up by a single comma. Of course, this priority does not apply to the GMAT, hence the recommendation of using serial commas wherever applicable.

2. Comma usage when combining two independent clauses

An independent clause includes a subject and verb, and can typically stand alone as a unique sentence. When combining two of these in a single sentence, it’s important to remember to separate each independent clause with a comma (often by placing a comma before “and”). Consider the following example below.

[Casey has 15 years of experience in professional kitchens], and [today she is opening her first restaurant].

We’ve bracketed each independent clause to highlight the fact that each one would be a grammatically correct sentence on its own. Each one has a clear subject and a verb, making the comma before “and” a coordinating device that neatly combines the two into one sentence. On the other hand, a comma is not necessary when combining an independent clause with a dependent clause. We’ve rewritten the previous sentence to give you an example below.

Casey attended culinary school for 2 years and is a celebrated chef today.

While the content in both sentences is similar, there is a major difference between our first and second examples. In the first example, we were able to separate each independent clause in brackets, and both could operate as separate sentences on their own. However, even though we have two verbs in the rewritten example (attended, is), we only have one subject (Casey), making a comma unnecessary in this case.

Thanks for reading! Stay tuned for more in-depth explanations of the many parts of GMAT Verbal and Quant.

This post appeared first on the Economist GMAT Tutor blog.


  • can you send me some more examples of the same kind 

  • In the final example: "Casey attended culinary school for 2 years and is a celebrated chef today." If we modify this sentence as I did below, would the sentence require the comma that I added to be grammatically correct?

    "Casey attended culinary school for 2 years, and SHE is a celebrated chef today."

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