Day 189: Two-part sentences need to be parallel.

A two-part sentence has two phrases or clauses that depend on each other to provide information. Consider this two-part sentence.

“The hybrid engine runs smoothly and burns fuel efficiently.”

The first part is “runs smoothly.” The second part is “burns fuel efficiently.” They are parallel, which means they use the same grammatical structure. Now consider this sentence.

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“Students learn more when they participate than by listening to the teacher.”

The first part is “when they participate.” The second part is “by listening to the teacher.” These two parts are not parallel; they do not have the same grammatical structure. Either both parts need to have the “when they [verb]” structure or they need the “by [-ing verb]” structure. When we make the two parts parallel, we get the following sentences.

“Students learn more when they participate than when they listen to the teacher.”
“Students learn more by participating than by listening to the teacher.”