There’s an old saying that mentions “comparing apples to oranges.” The implication of that saying is that it is undesirable to compare dissimilar things in real life. For instance, comparing the score improvements of 2 students preparing for the GMAT would be comparing apples to oranges, particularly if, for instance, one student was an experienced test-taker with the luxury of devoting several hours a day to studying, while the other was new to standardized testing and had many other time commitments that impeded studying. You want to compare apples to apples—instead of comparing your improvements to someone else’s, compare your scores only to your past performances. That’s your best gauge of progress, and it prevents you from comparing your “apples” to someone else’s “oranges.”
This theory is just as important in GMAT sentence corrections as it is in real life. When items are being compared, they must be “apples to apples,” or parallel. For instance, take a look at the following example of a comparison:
Unlike a standard mortgage, which allows the home-buyer to finance her purchase through a bank, land contract purchasers are financed directly by the property seller.
The sentence as written compares “a standard mortgage” to “land contract purchasers.” Mortgages are things, and purchasers are people or entities; this is an apples-to-oranges comparison. In order to correct it, we should put the items being compared into parallel form, like this:
Unlike a standard mortgage, which allows the home-buyer to finance her purchase through a bank, land contracts provide financing directly from the property seller.
But wait! Parallelism isn’t just about putting items in similar forms—they must also, as much as possible, be in similar numbers. We shouldn’t compare “a standard mortgage” to “land contracts” when we can compare it to “a land contract.” So the final, truly parallel sentence will look like this:
Unlike a standard mortgage, which allows the home-buyer to finance her purchase through a bank, a land contract provides financing directly from the property seller.
It’s not just items being compared that need to be parallel, though; items in a list must also be in parallel forms, and you’re actually more likely to see this kind of parallelism tested on the GMAT. Here’s an example:
Self-contained housing developments are significantly different from traditional neighborhoods, as their organization drastically reduces traffic from outside sources, encourages a higher level of uniformity in building construction and landscaping, and caused the emergence of nearby shopping areas.
The list in this sentence describes ways that self-contained housing developments differ from traditional neighborhoods. The first task is to check to make sure that the listed items are in similar forms. Each of the phrases in the list begins with a verb: “reduces,” “encourages,” and “caused.” But again, just being in the same form isn’t enough; here we need to make sure that, as long as revision doesn’t have a confusing impact on the meaning of the sentence, the verbs are all in the same tense. There’s no reason to think that “nearby shopping areas” emerged in the past but have ceased to do so now, since one can assume that housing developments are still being built. Therefore, the sentence can be revised into the following parallel format:
Self-contained housing developments are significantly different from traditional neighborhoods, as their organization drastically reduces traffic from outside sources, encourages a higher level of uniformity in building construction and landscaping, and causes the emergence of nearby shopping areas.
That one letter difference, from “caused” to “causes,” is the difference between getting a question right and getting it wrong. So what can you, the intrepid test-taker, do to ensure that parallelism isn’t a problem for you on the GMAT?
- Scan sentences for comparisons or lists. Often, longer sentences contain lists of phrases, so that can be a clue, but just try to get into the habit of looking for comparisons and lists in every sentence correction question.
- Put items in similar forms: nouns are listed with nouns, verbs with verbs, etc.
- Make sure that numbers and tenses match up, as well as any other issues at impact parallelism.
Every sentence correction question that contains a comparison or a list should be your cue to take an inventory of what is being compared or listed. Then you need to watch out for consistent verb tenses, double-check for parallel singular or plural construction, and confirm that there are no other grammatical issues that interfere with parallel structure.
[For instance, in the paragraph above, you might notice the pairing of “a comparison” and “a list,” as well as the consistent tenses and forms of “watch out,” “double-check,” and “confirm,” all as examples of parallelism.]
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