Skip to main content

TIP 6. Express Coordinated Ideas in Parallel Form

Express coordinated ideas in a similar form. Parallels in substance are reinforced by parallels in structure.

GOOD EXAMPLES OF PARALLEL CONSTRUCTIONS

The inherent vice of capitalism is the unequal sharing of blessings; the inherent virtue of socialism is the equal sharing of miseries.
Winston Churchill

The mechanism is thought to be due to decreased bile flow, changes in the tight junctions between the cells, and altered fluidity of the hepatocyte junction.
Former class participant

Churchill's sentence is a splendid example of high rhetoric, but the same technique of parallel construction can be used in scientific writing, as shown by the second example. This sentence works as a parallel construction because each of the three listed items is in the same part of speech ("bile flow," "changes," and "fluidity" are all nouns). Moreover each of these nouns is modified ("decreased," "in tight junctions," and "altered.") Hence the ear can hear the parallel construction, and the mind interprets the items as a coherent list. Such sentences are very useful for summarizing complex ideas in a list within a sentence, and are commonly used in scientific writing.



EXAMPLE 19. Plasmin, a protease, plays a significant role not only in degrading fibrin, but also as a regulator of tissue repair and remodeling.

Rev 19. Plasmin is a protease that plays a significant role not only in degrading fibrin, but also in regulating tissue repair and remodeling.

Note on Example 19: Here the words "not only" and "but also" mandate the use of a parallel construction. However, the author does not put "degrading" and "regulator" in the same part of speech. This problem is easy to fix. If we change "regulator" to "regulating," it will be parallel to "degrading." [The alternative, changing "degrading" to "degrader" would sound awkward.]


EXAMPLE 20. The urea-induced conductance completely reversed upon removal of urea, was non-selective, and the magnitude was voltage dependent.

Rev 20a. The urea-induced conductance was non-selective, voltage-dependent, and completely reversible.

Rev 20b. The urea-induced conductance was non-selective and varied with voltage. The effect was completely reversed upon removal of urea.

Note on Example 20: This parallel construction is flawed because the three items in the list do not match: "completely reversed" is a verb, "non-selective" is an adjective, and "magnitude" is a noun. The first revision makes the list parallel. The second version says more about the third item and therefore puts that element in its own sentence. Parallel constructions work best if the listed items are fairly simple and similar in content.


EXAMPLE 21. Adherence ranges from 10-30% for simple interventions, more intensive interventions result in higher rates of up to 50%.

Rev 21. For simple interventions, adherence rates range from 10-30%, while for more intensive interventions, adherence rates can reach 50%.

Note on Example 21: This rather simple sentence does not cry out for revision, but the revision shows the best technique for organizing information in lists that contain numbers. For maximum clarity, place the contextual descriptor first (e.g. "For simple interventions"), the specific descriptor second (adherence rates), and the number last (10-30%). Varying the order of these parts with parallel items invites confusion (as in the next example).


EXAMPLE 22. Given a prevalence of osteoporosis of 10.8% (similar to previous reports), the predictive value positive and negative for the ORAI were 19.7% and 94.5% respectively. These compare to a predictive value positive of 19.0% and a predictive value negative of 92.9% for the SCORE instrument.

Rev 22a. Given our finding that the prevalence of osteoporosis was 10.8% (similar to previous reports), the positive and negative predictive values for the ORAI were 19.7% and 94.5% respectively, while for the SCORE instrument they were 19.0% and 92.9%.

Rev 22b. We found that the prevalence of osteoporosis was 10.8%, a result consistent with previously reported findings. The positive and negative predictive values for the ORAI and the SCORE were very similar: 19.7 and 94.5% respectively for the ORAI, and 19.0 and 92.9% for the SCORE.

Note on Example 22: This is a very challenging sentence to compose, because it contains an embedded list with two sets of data per item. It is like a table built into a sentence. Each item needs two descriptors ("positive predictive value" and "negative predictive value"), and also two numbers (e.g., "19.7%" and "94.5%"). Hence strict adherence to the rules presented in the Note on Example 21 is obligatory. We offer two revisions. The first lines up the numbers in parallel and eliminates redundant verbiage. The second revision does the same, but in addition it tells the reader up front what to expect from the data. When the main point is that the numbers are similar, why make the reader figure that out?


EXAMPLE 23. Abdominal pain, a common complaint in childhood, may be a symptom of an acute or even catastrophic intra-abdominal process, an indicator of a chronic physiologically based malfunction of the viscera or a reflection of an abdominal organ as the target of psychological stresses perceived by the complaining child.

Rev 23a. Abdominal pain, a common complaint in childhood, may be a symptom of an acute or even catastrophic intra-abdominal process, an indicator of a chronic malfunction of the viscera, or a reflection of psychological stresses perceived by the complaining child.

Rev 23b. Abdominal pain, a common complaint in childhood, requires careful physical and psychological assessment of the patient. Occasionally the pain may reveal an acute (or even catastrophic) intra-abdominal process, or a chronic, physiologically based intestinal malfunction. More often, abdominal pain reflects a child's tendency to target the stomach as the focal point of psychological stresses.

Note on Example 23: This sentence attempts to create a parallel construction and it achieves grammatical parallelism ("symptom," "indicator," and "reflection" are all nouns). However, the author has different things to say about each item, so the list is difficult to "hear" and thus understand easily. The first revision simplifies the three items so they work better in parallel. The second abandons the parallel construction and lets each item go in its own direction.


EXAMPLE 24. The Pew Commission was particularly forceful in its calls for changes in curricula, suggesting that innovations were needed to redefine courses of study to provide for core instruction and to emphasize that educational programs should be organized around competencies.

Rev 24a. The Pew Commission was particularly forceful in its calls for changes in curricula, suggesting that innovations were needed 1) to redefine courses of study that provide for core instruction and 2) to organize educational programs around competencies.

Rev 24b. The Pew Commission was particularly forceful in its calls for changes in curricula, suggesting that innovations were needed to redefine courses of study that provide for core instruction. They also emphasized that educational programs should be organized around competencies.

Note on Example 24: This sentence sounds like a parallel construction and one can try to read it as a three-part list ("to redefine," "to provide," "to exercise"), but it just doesn't make sense this way. The phrase "to provide for core instruction" creates a parallelism in sound that fails to match a parallelism in meaning: this phrase really means "courses of study that provide for core instruction." The first revision creates a workable two part parallel construction. The second revision abandons parallelism and divides the example into two separate sentences.