Parallel structures commonly result in economy of words, clearer meaning, and pleasing effects. Parallelism of ideas is most frequent in phrases, but can also be in clauses and other word combinations, such as compound subjects and predicates (the part of a sentence that makes a statement about the subject). Some of the most valuable uses pertain to descriptions and involve whole sentences and paragraphs:

With compound subjects, the individual subjects should have the same form:

With compound predicates, be sure the verbs are correct and in the same tense throughout:

For items in lists, give parallel information in parallel forms:

Even though the missing information may have little importance, sentences such as the second last can give readers wrong impressions, or throw them off stride and break their concentration. A more exaggerated example:

Parallel structure is especially useful for making detailed descriptions and comparisons more readable. For example, if the different minerals in a rock are always described with their features (such as modal abundance, grain size, and habit) in the same order, then readers can assimilate the information more easily. As well, when two rocks are compared by presenting their features in parallel groups (say of three), readers will not have to switch back and forth as much between the two descriptions. It may even be helpful to construct successive paragraphs in parallel.