What is Grammatical Parallelism and Why It Matters

What is Grammatical Parallelism and Why It Matters

Clear, correct writing is a baseline expectation in scholarly work. Editors, reviewers, funders, students, and colleagues all read for precision and coherence—especially when ideas are complex. One of the most reliable tools for achieving that clarity is grammatical parallelism. Parallelism aligns the grammatical form of related items so readers can process information more quickly and accurately. It improves style, reduces ambiguity, and signals professional care. This post explains what parallelism is, why it matters in academic and scientific writing, and how to apply (and repair) it across sentences, lists, headings, methods, and figure legends.

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What Is Grammatical Parallelism?

Grammatical parallelism occurs when two or more elements in a sentence (or across consecutive sentences) share the same syntactic form. The elements may be words, phrases, or clauses. When the form is consistent, the reader’s brain spends less effort decoding structure and more effort understanding content.

Basic example (parallel):
The professor teaches in the lecture hall, provides tutorials in the office, and offers writing advice online.

Non-parallel (awkward and potentially ambiguous):
The professor teaches in the lecture hall, provides tutorials in the office, and on the university website offers writing advice.

In the non-parallel version, the third item breaks the pattern, forcing readers to reparse the sentence and momentarily misattach “on the university website.” Restoring parallel structure removes the ambiguity.

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Why Parallelism Matters in Academic & Scientific Writing

• Comprehension: Readers grasp lists, comparisons, and multi-step procedures faster when the form repeats.
• Persuasion: Balanced structure gives arguments rhythm and authority, especially in abstracts, key claims, and conclusions.
• Accuracy: Parallelism reduces grammatical mismatches that can distort meaning (e.g., tense, voice, or subject changes mid-list).
• Professionalism: Journals expect consistent style in headings, bullet lists, table stubs, and figure captions.

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Core Patterns of Parallelism (with Fixes)

1) Parallelism in Simple Series

Use the same grammatical form for each item: all gerunds, all infinitives, or all base verbs.

• Non-parallel: She loves reading, writing, and to teach.
• Parallel (option A): She loves reading, writing, and teaching.
• Parallel (option B): She loves to read, to write, and to teach.

2) Modals and Complements

Keep complements consistent after modals and auxiliaries.

• Non-parallel: The article must be well written, carefully researched, and follow the guidelines.
• Parallel: The article must be well written, carefully researched, and consistently formatted.
• Parallel (split into two): The article must be well written and carefully researched, and it must also follow the guidelines.

3) Correlative Conjunctions

Correlatives (not only… but also, either… or, neither… nor, both… and) require symmetry on both sides.

• Non-parallel: Not only did the model improve prediction, but also generalisability increased.
• Parallel: Not only did the model improve prediction, but it also increased generalisability.

4) Comparatives

Make sure what you compare shares form and category.

• Non-parallel: The new assay is faster than the previous method was cost-effective.
• Parallel: The new assay is faster than the previous method is cost-effective. (still clunky)
  Better: The new assay is faster, whereas the previous method is more cost-effective.

5) Infinitives and Split Infinitives

Traditional academic style often avoids splitting “to” + verb with an adverb when a smooth alternative exists.

• Preferred: to write effectively
• Less preferred (but increasingly accepted if clearer): to effectively write

6) Parallel Verbs for Chronology

Align tense and aspect when describing steps or concurrent actions.

• Parallel steps: We recruited participants, randomised them, and analysed outcomes.
• Mixed (confusing): We recruit participants, randomised them, and have analysed outcomes.

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Parallelism Across Academic Genres

Abstracts

Many journals expect abstracts to follow a predictable sequence (background → objectives → methods → results → conclusions). Use parallel sentence openings and verb forms to signpost those moves.

• Example: We aimed to… We conducted… We found… We conclude…

Methods & Protocols

Consistency aids reproducibility. Keep the same voice, tense, and order across subsections.

• Parallel headings: Participants; Materials; Procedure; Analysis
• Parallel actions: We measured X, controlled Y, and computed Z.

Figures & Tables

Readers scan captions and table stubs quickly. Parallel phrasing improves skim value.

• Captions (parallel verbs): Figure 2 shows…, Figure 3 compares…, Figure 4 maps…
• Table stubs: Baseline characteristics; Intervention effects; Sensitivity checks (all noun phrases).

Bullet Lists

Start each bullet with the same part of speech (all nouns, all -ing forms, or all imperatives). End punctuation should be consistent within the list.

• Parallel (gerunds): Defining variables; Cleaning data; Validating models
• Parallel (imperatives): Define variables. Clean data. Validate models.

Headings & Subheadings

Journals often require consistent heading grammar (all noun phrases or all -ing forms). Parallel headings double as an outline and improve navigation.

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Recognising and Repairing Non-Parallel Structure

Diagnosis Tips

• Underline the pattern: Identify the repeated grammatical slot (e.g., verb + object). Does each item fill it the same way?
• Test by deletion: If you remove the first two items, does the remaining item still attach grammatically to the stem?
• Check symmetry triggers: Correlatives (either/or), comparatives (more… than…), and series after a colon frequently expose breaks in parallelism.

Repair Moves

1. Match the form: Rewrite outliers to match the dominant pattern (all gerunds, all infinitives, all finite clauses).
2. Re-punctuate: Use a semicolon or an em dash to separate a clause that does not naturally parallel the list.
3. Split the sentence: If one item is inherently different, give it its own sentence to avoid forcing a false parallel.

Before/After Repairs

Before: The intervention reduces wait times, to improve satisfaction, and was associated with lower costs.
After (verbs aligned): The intervention reduces wait times, improves satisfaction, and lowers costs.

Before: Our aims are to test hypothesis 1, testing hypothesis 2, and we also examine moderators.
After (infinitives): Our aims are to test hypothesis 1, to test hypothesis 2, and to examine moderators.

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Advanced Parallelism for Style & Emphasis

Antithesis (balanced contrast)

Parallelism heightens contrast and memorability in claims and conclusions.

• We measured efficacy in the lab and effectiveness in the field.
• The approach is simple to implement but powerful in effect.

Isocolon (equal-length units)

Equal structure and similar length add rhetorical weight to abstracts and lay summaries.

• We collect the data, we model the pattern, we test the claim.

Parallel Paragraph Openings

In literature reviews or multi-part arguments, parallel first sentences help readers map the structure.

• First, prior work establishes…
• Second, recent evidence suggests…
• Third, our data indicate…

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Disambiguating Meaning with Parallelism

Parallel structure prevents attachment errors and reduces misreadings in long sentences.

Ambiguous: We interviewed clinicians in person, by telephone, and emails were also sent.
Parallel: We interviewed clinicians in person, by telephone, and by email.

Ambiguous: The model improves recall in oncology and cardiology performs worse.
Parallel: The model improves recall in oncology but performs worse in cardiology.

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Parallelism Across Tense, Voice, and Person

• Tense: Keep parallel tenses in methods and results. If you switch, signal the reason (past for actions taken; present for general truths).
• Voice: Avoid mixing passive and active within one patterned list unless contrast is intended.
• Person: If you use “we,” keep it; do not drift to impersonal “the authors” within the same structure.

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Parallelism in Headings, Captions, and Table Labels

Element	Non-parallel	Parallel
Section Headings	Recruitment; Inclusion Criteria; How We Analysed	Recruitment; Inclusion Criteria; Analysis
Figure Captions	Figure 1: Baseline distribution; Figure 2: We compare cohorts	Figure 1: Shows baseline distribution; Figure 2: Compares cohorts
Table Stubs	Outcomes; To estimate effects; Sensitivity	Outcomes; Effect Estimates; Sensitivity Analyses

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A Quick Editorial Workflow for Parallelism

1. Scan for series: Commas with “and/or” usually mark candidates. Ensure like form across items.
2. Locate correlatives: Check that each side mirrors the other in grammar and logic.
3. Audit headings & bullets: Align part of speech and end punctuation.
4. Check methods/results verbs: Make step lists parallel in tense and voice.
5. Re-test ambiguous attachments: If an item seems to “lean” on the wrong word, rebuild the pattern.

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Practice: Repair These for Parallelism

1. The study aims to evaluate adherence, measuring satisfaction, and we also compare clinics.
2. Participants were randomised, baseline is collected, and we analysed outcomes.
3. Both improving accuracy and to reduce cost are priorities.
4. We tested in mice, in vitro experiments were completed, and ran simulations.

One set of possible fixes:

1. The study aims to evaluate adherence, to measure satisfaction, and to compare clinics.
2. Participants were randomised, baseline data were collected, and outcomes were analysed.
3. Both improving accuracy and reducing cost are priorities.
4. We tested in mice, conducted in vitro experiments, and ran simulations.

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When Is It Okay to Break Parallelism?

Purposeful variation can improve rhythm or highlight an exception—provided grammar remains correct and the meaning stays clear. For example, you might interrupt a list with a short emphatic sentence, or switch from nouns to a clause to accommodate a necessary caveat. Use this sparingly; clarity comes first.

Controlled variation:
We define the variables, specify the priors, and—because the pilot suggested instability—estimate a regularised model.

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Checklist for Your Next Manuscript

• [ ] Items in lists and series share the same grammatical form.
• [ ] Correlative pairs (either/or, not only/but also) are balanced on both sides.
• [ ] Headings, bullets, and table labels use consistent part of speech and punctuation.
• [ ] Methods and results steps use parallel tense and voice.
• [ ] Abstract sentences use a consistent move structure (aim → method → result → implication).
• [ ] Ambiguities from broken parallelism are eliminated.

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Final Thoughts

Grammatical parallelism is not decoration; it is a cognitive aid. In dense scholarly prose, repeated form reduces processing load, strengthens emphasis, and prevents errors from creeping into lists, captions, and claims. When you align structure—across series, correlatives, headings, and procedural steps—you make your work easier to read, cite, and trust.

If you’d like expert help reviewing parallelism, structure, and journal style before submission, professional academic editors at Proof-Reading-Service.com can polish manuscripts so your ideas stand out—and your grammar disappears into clarity.