Simple explanation
What is parallelism? Parallelism occurs when two or more elements with equivalent grammatical or semantic functions are expressed through comparable structures. For example, a sequence such as to analyse the evidence, to challenge the assumptions, and to revise the conclusion is structurally consistent because each item uses the same infinitive pattern. At C2 level, parallelism is not merely a matter of avoiding error. It is also a tool for controlling rhythm, emphasis, readability, and rhetorical force. Parallelism in coordinated structures Elements linked by and, or, but, yet, and similar conjunctions are easier to process when they operate at the same syntactic level. Noun phrases usually coordinate most naturally with noun phrases, gerunds with gerunds, infinitives with infinitives, and clauses with comparable clauses. Mixed structures are not always ungrammatical, but unnecessary shifts in form often make a sentence feel unstable or difficult to interpret. Parallelism with correlative conjunctions Structures such as both...and, either...or, neither...nor, whether...or, and not only...but also require especially careful balancing. The material following each half should normally have the same syntactic status. Placement matters as much as form: if not only introduces a verb phrase, but also should generally introduce a corresponding verb phrase rather than a noun phrase or clause of a different type. What is syntactic balance? Syntactic balance goes beyond simple grammatical matching. Two sentence parts may be technically parallel but still feel uneven if one is short and direct while the other is heavily embedded or overloaded with detail. Skilled writers balance length, complexity, informational density, and rhetorical importance so that connected or contrasted elements feel proportionate. Parallelism in comparisons Comparative structures require both syntactic and logical equivalence. A sentence should compare like with like. For example, The salary of senior researchers is higher than that of junior researchers is more precise than a structure that compares salary directly with researchers. At advanced levels, writers should examine not only the form of comparisons but also the actual entities being compared. Parallelism as a rhetorical device Parallelism can create rhythm, emphasis, and cohesion in speeches, essays, academic prose, and literary writing. A sentence such as We questioned the evidence, challenged the methodology, and rejected the conclusion gains force from the repetition of the verb-plus-object pattern. Parallelism is especially effective in antithesis, where structurally similar parts express sharply contrasting ideas. When asymmetry is acceptable Not every departure from parallel structure is an error. Deliberate asymmetry may be used to create surprise, shift emphasis, disrupt rhythm, or foreground a final idea. At C2 level, the key distinction is intentionality. A marked structure can be effective if the change serves a clear rhetorical purpose; accidental inconsistency usually weakens clarity and control.
Grammar formula
Parallel base verbs
verb + X, verb + Y, and verb + ZThe reform aims to simplify procedures, reduce costs, and improve accountability.
Parallel gerunds
gerund + X, gerund + Y, and gerund + ZEffective leadership involves listening carefully, responding decisively, and adapting quickly.
Both...and
both + parallel element A + and + parallel element BThe proposal is both financially viable and politically acceptable.
Not only...but also
not only + parallel element A + but also + parallel element BThe policy not only reduced expenditure but also improved service quality.
Either...or
either + parallel element A + or + parallel element BWe can either revise the methodology or repeat the experiment.
Balanced comparison
X + comparative + than + equivalent form of YThe performance of the revised model was better than that of the baseline.
Balanced antithesis
parallel structure A + contrast marker + parallel structure BThe aim is not to eliminate uncertainty but to manage it intelligently.
Core rules
- 1
Match elements that perform the same function
If several elements are grammatically and semantically equal, keep their structures comparable. A sequence such as analysing, comparing, and interpreting is usually clearer than a mixture of analysing, to compare, and interpretation.
- 2
Align both halves of correlative structures
With both...and, either...or, neither...nor, and not only...but also, position each marker immediately before the elements being balanced whenever possible.
- 3
Maintain consistent verb patterns in lists
If a list begins with base-form verbs, gerunds, or infinitives, avoid changing the pattern without a clear reason. Consistency reduces processing effort and improves stylistic control.
- 4
Compare equivalent things
Parallelism in comparisons requires logical equivalence. Make sure the sentence compares a person with a person, a result with a result, a process with a process, or another genuinely corresponding pair.
- 5
Balance rhetorical weight as well as grammar
Two parts may be grammatically parallel but stylistically unbalanced. Consider whether they are reasonably similar in length, complexity, emphasis, and informational importance.
- 6
Use ellipsis only when clarity survives
Repeated words or structures can often be omitted, but the remaining sentence must still make the parallel relationship obvious. Excessive ellipsis can create ambiguity or false coordination.
Useful examples
The committee sought to reduce administrative costs, improve transparency, and strengthen public trust.
The committee wanted to cut costs, make processes more transparent, and build greater public confidence.
All three objectives are expressed through parallel base-form verbs.
She is respected not only for her technical expertise but also for her ability to explain complex ideas clearly.
People value her both for her specialist knowledge and for the way she explains difficult ideas.
The two for-phrases are structurally parallel.
The new framework is both theoretically coherent and empirically testable.
The framework makes sense in theory and can also be tested through evidence.
Both and and link two adjective phrases of equal grammatical status.
We can either refine the existing model or develop an entirely new architecture.
Our options are to improve the current model or create a completely new architecture.
The alternatives are expressed through matching verb phrases.
What matters is not how quickly we reach a conclusion but how carefully we justify it.
The important issue is not speed, but the quality of the reasoning behind the conclusion.
Two parallel how-clauses create a clear contrast.
The revised system is easier to deploy, cheaper to maintain, and more reliable under heavy load.
The new version can be deployed more easily, maintained at lower cost, and trusted more under demanding conditions.
The three complements are structurally comparable and rhetorically balanced.
The performance of the multilingual model was stronger than that of the monolingual baseline.
The multilingual model performed better than the monolingual baseline did.
That of ensures that performance is compared with performance.
The researchers questioned the assumptions, challenged the methodology, and rejected the original interpretation.
The researchers disputed the assumptions, criticised the method, and dismissed the first interpretation.
The repeated verb-plus-object pattern creates rhythm and emphasis.
Her argument was concise without being simplistic, rigorous without being inaccessible, and critical without being dismissive.
Her argument was brief but not oversimplified, demanding but still understandable, and critical without becoming disrespectful.
Each segment follows the same adjective plus without being pattern.
We need policies that are ambitious enough to drive change yet realistic enough to survive implementation.
Policies must be bold enough to produce change but practical enough to work in reality.
The two enough to structures form a balanced contrast.
The question is not whether the technology will evolve, but whether institutions will evolve with it.
The issue is not whether technology will change, but whether institutions will change alongside it.
Two parallel whether-clauses create a controlled antithesis.
To understand the failure is to examine the incentives, to reconstruct the decisions, and to identify the assumptions behind them.
Understanding the failure requires examining the incentives, reconstructing the decisions, and identifying the assumptions involved.
Three parallel infinitive phrases produce a formal analytical rhythm.
The reform promised greater efficiency, broader access, and a fairer distribution of resources.
The reform was intended to improve efficiency, expand access, and distribute resources more fairly.
The three noun phrases are balanced in both grammar and meaning.
They were willing to negotiate, prepared to compromise, but unwilling to abandon their core principles.
They accepted negotiation and compromise but refused to give up their fundamental principles.
Three adjective complements form a parallel sequence, while but highlights the final contrast.
Common mistakes
- ❌ The position requires analysing data, writing reports, and to present findings. ✅ The position requires analysing data, writing reports, and presenting findings. All three activities have the same function after requires, so they should use the same gerund pattern.
- ❌ The initiative aims to reduce waste, improving efficiency, and greater transparency. ✅ The initiative aims to reduce waste, improve efficiency, and increase transparency. The original version mixes a base verb, a gerund, and a noun phrase within a single list.
- ❌ She not only identified the problem but also a practical solution. ✅ She identified not only the problem but also a practical solution. The corrected position makes not only and but also introduce two parallel noun phrases.
- ❌ The salary of experienced engineers is higher than junior engineers. ✅ The salary of experienced engineers is higher than that of junior engineers. The incorrect version compares salary with engineers. That of creates a logical salary-to-salary comparison.
- ❌ The report was clear, comprehensive, and it provided useful recommendations. ✅ The report was clear, comprehensive, and useful. If the purpose is to list three qualities of the report, three adjective complements provide a cleaner parallel structure.
- ❌ We need either to delay the launch or a reduction in scope. ✅ We need either to delay the launch or to reduce the scope. The two alternatives are more balanced when both are expressed as infinitive phrases.
- ❌ The new model is more accurate than the accuracy of the previous model. ✅ The new model is more accurate than the previous model. The incorrect sentence compares a model with an accuracy measure rather than comparing two models.
Learning tips
- When checking a three-part list, compare the full grammatical units rather than only their first words.
- With not only...but also, identify exactly which two elements are being coordinated before deciding where to place the markers.
- In academic writing, parallelism helps readers identify relationships among claims, methods, findings, and implications.
- If a sentence is grammatically parallel but still sounds awkward, examine the relative length and complexity of its parts.
- Use rhetorical parallelism to create progression, not mechanical repetition.
- In comparisons, always ask what is actually being compared with what.
- At C2 level, do not automatically remove every asymmetry. First decide whether the structural break is intentional and rhetorically useful.
Practise this topic
Interactive exercises for this topic are coming soon.
PlannedRelated grammar
Related dictionary words
Frequently asked questions
Do parallel elements have to contain exactly the same number of words?
No. Parallelism depends primarily on grammatical function and structural equivalence, not word count. However, extreme differences in length or complexity can make a sentence feel rhetorically unbalanced.
Can an adjective be parallel with an adjective phrase?
Yes. Elements such as secure and easy to maintain can be parallel if both serve the same grammatical function, for example as complements of be. Parallelism concerns syntactic role rather than superficial length.
What is the difference between parallelism and repetition?
Repetition simply means that words or patterns recur. Parallelism is the organised use of corresponding grammatical structures for related ideas. A sentence can therefore be parallel without repeating exactly the same words.
Why does the position of not only matter?
Its position shows which element is being paired with the element after but also. Poor placement can connect structures of different grammatical types or change the intended meaning.
Is lack of parallelism always a grammatical error?
No. In neutral formal writing, unnecessary asymmetry is often a structural or stylistic weakness. In literary or rhetorical writing, however, a deliberate break in pattern can create emphasis, surprise, or a change in rhythm.
Is parallelism only important in long sentences?
No. Even short sentences such as She is calm, precise, and persuasive benefit from parallel structure. The principle becomes especially useful in longer sentences because it helps readers process complex relationships more efficiently.
How can I detect parallelism problems when editing?
First identify lists, coordinating conjunctions, comparisons, and correlative constructions. Then determine the grammatical function of the elements being linked. Finally, compare their length, complexity, semantic weight, and logical relationship.