Parallel structure at the sentence level
Earlier we discussed the idea of parallel structure at the document level. There, it referred to structural issues such as maintaining the same level of heading for document components of equal importance.
At the sentence level, parallel structure can take several different forms: single words, phrases, or clauses. As always, it is based on the principle that elements that are similar in function should be similar in form. It particularly shows up—or should show up—in two kinds of situations: lists and comparisons. Parallel structure is evident both in a sentence's grammatical structure and in its visual presentation.
Parallel structure is not only a grammatical structure, it is also a very good way to organize the information in your sentences and paragraphs. Recognizing the parallelism allows your readers to predict more easily the form and the flow of your ideas. Have a look below at some examples of poor parallel structure, and then click with your mouse on each example to see an improved version.