A 2 min read

A sentence often presents a list of ideas expressed using series of words, phrases, or clauses.  These series talk about one common topic. For such sentences, we need to maintain parallelism i.e. all elements in the series must be written in same grammatical form. For example:

Mary cooked food, laying the table, and cleaning the house before the guests arrived.

This sentence presents a list of activities that Mary performed before the guests arrived.  Thus, all these activities should be written in parallel form.  However, notice that they are not written in parallel form

• cooked
• laying
• cleaning

This is a list of verbs and all should be expressed in same verb tense.  In this sentence, they should all be listed in simple past tense to express the intended meaning.  The correct sentence is:

Mary cooked food, laid the table, and cleaned the house before the guests arrived.

Lets take another example:

Even though Tom is not interested in arts, he would rather visit an arts museum than listening to his annoying wife.

The author intends to show a comparison in this sentence – preference of Tom.  The author compares two actions of Tom –  “visit an arts museum” & “listening to his annoying wife”.  Thus, these two actions should be expressed in grammatically parallel form.  The correct sentence is:

Even though Tom is not interested in arts, he would rather visit an arts museum than listen to his annoying wife.

In the two examples above, we were able to logically detect the presence of list.  In sentence 1, list was present because the sentence presented list of actions performed by Mary.  In sentence 2, the list was present because of the stated preference or comparisons of Tom’s actions.

In addition to logically determining the the presence of list, we can also make this determination by looking out for certain marker words such as and, or, but.  Expressions such as either..or, neither..nor, both..and, etc. also signal that the sentence should be written in parallel form.

Parallelism errors are one of the most frequently tested errors on GMAT.  These errors are covered in detail in the module “Parallelism” in e-GMAT SC course:

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