Parallelism Usage Rules

By this stage you already recognize parallel structure when a sentence lists gerunds, infinitives, or clauses in a series. Standardized grammar and sentence correction questions rarely ask you to define parallelism directly; instead they bury a broken pattern inside a longer sentence and ask you to choose the answer choice that repairs it without introducing a new error. This lesson focuses on the rules test writers rely on most often and on a repeatable method for applying them under time pressure.

Sentence correction items typically disguise parallelism errors in three locations: a series of three or more items, a pair joined by a correlative conjunction, or a comparison built with than or as. Because only part of the sentence is underlined, you must first decide which words outside the underline set the grammatical pattern the underlined portion has to match. Skipping this step is the single most common reason students choose an answer that "sounds fine" but is still grammatically inconsistent.

Correlative conjunctions work in fixed pairs: not only and but also, either and or, neither and nor, both and and, whether and or. The rule is strict: whatever grammatical form follows the first half of the pair must be repeated after the second half. If not only is followed by an adjective, but also must be followed by an adjective as well, not by a full clause.

For a closer look at how these pairs behave inside a single sentence, see Parallelism in Sentences.

Comparisons built with than or as require the two elements being compared to share the same grammatical form. "Learning to write clearly is as valuable as reading critically" is parallel because two gerund phrases are compared. A sentence that shifts to "Learning to write clearly is as valuable as to read critically" breaks the pattern by switching from a gerund phrase to an infinitive phrase. Test writers frequently exploit this shift because the sentence still sounds acceptable when read quickly.

Apply the following sequence to any question that tests parallelism:

1. Locate the coordinating element: a series, a correlative pair, or a comparison.

2. Identify the grammatical form established by the first item, before any underline.

3. Check every remaining item in the series or pair against that established form.

4. Eliminate any answer choice that breaks the pattern before comparing the survivors for concision and clarity.

Working in this order prevents you from being distracted by an answer choice that fixes grammar but adds unnecessary wording, or one that sounds smooth but quietly shifts form partway through the sentence.

Three trap patterns appear repeatedly on these questions. The first repairs only one item in a series of three, leaving a second item mismatched. The second corrects the grammatical form but changes verb tense inconsistently across the series. The third replaces a broken phrase with a full clause, creating a new parallelism error where the original error is removed but a fresh imbalance is introduced. Reading the entire sentence, not just the underlined section, is the only reliable way to catch these substitutions.

Example: "The proposal was praised for being thorough, well researched, and it persuaded the board." A revision that changes only "it persuaded" to "persuasive" fixes the series, while a revision that changes it to "for persuading the board" introduces a fourth, differently shaped item. Applying the four step strategy above catches both possibilities before you commit to an answer. For additional practice building and revising longer parallel passages, see Parallel Structure in Writing.

Related lessons

• Parallel Structures