Maintain grammatical parallelism in lists, comparisons, and correlative constructions. Create balanced, professional sentences.
约6分钟阅读
Parallel structure -- also called parallelism -- means using the same grammatical form for words, phrases, or clauses that serve the same function in a sentence. When you write a list, a comparison, or a pair of ideas, each element should follow the same pattern.
Parallelism is one of the most powerful tools in a writer's toolkit. It makes your sentences clearer, more balanced, and more persuasive. At the same time, breaking parallelism is one of the most common errors in student writing, and it is specifically tested in IELTS, TOEFL, AP English, and standardized writing exams.
When two or more items are joined by a coordinating conjunction (and, but, or, nor) or appear in a list, they must share the same grammatical form.
| Not Parallel | Parallel |
|---|---|
| She likes reading, to swim, and bikes. | She likes reading, swimming, and biking. |
| The job requires experience, being creative, and you must be patient. | The job requires experience, creativity, and patience. |
| He is smart, has ambition, and a hard worker. | He is smart, ambitious, and hardworking. |
In each corrected version, every item in the list follows the same grammatical pattern: all gerunds, all nouns, or all adjectives.
Parallel structure makes it immediately clear that items belong together. When the pattern breaks, readers stumble.
Not parallel: The report was praised for its thorough research, it was written clearly, and accuracy of data.
A reader encountering this sentence has to mentally reorganize three different structures. Compare:
Parallel: The report was praised for its thorough research, clear writing, and accurate data.
Now all three items are noun phrases with the same adjective + noun pattern. The reader processes them effortlessly.
Parallelism creates a natural rhythm that carries readers through your sentence. This rhythm is especially important in persuasive and academic writing.
Flat: The company needs to reduce costs. They also should improve their products. And they need to be expanding into new markets.
Rhythmic: The company needs to reduce costs, improve products, and expand into new markets.
The parallel version has a satisfying cadence. Each item has the same weight and pace.
The most memorable lines in speeches, essays, and literature rely on parallelism:
"Government of the people, by the people, for the people." -- Abraham Lincoln
"I came, I saw, I conquered." -- Julius Caesar
"Ask not what your country can do for you -- ask what you can do for your country." -- John F. Kennedy
Parallelism gives these statements their power. Remove the parallel structure, and they lose their impact.
Exam rubrics explicitly reward grammatical accuracy and range. Faulty parallelism counts as a grammatical error in IELTS (Band 6 vs. Band 7 grammar criterion), TOEFL writing, and AP English. Correct parallelism demonstrates control of complex sentence structures, which is what evaluators look for in high-scoring essays.
Let's look at the most common grammatical forms that must stay consistent.
The curriculum covers mathematics, science, and history.
All three items are nouns. You would not write: "The curriculum covers mathematics, scientific study, and learning about history."
The manager reviewed the data, identified the trends, and presented the findings.
All three items are past-tense verbs. Each follows the same subject ("The manager") and takes a direct object.
The presentation was informative, engaging, and well-organized.
All three items are adjectives (or adjectival compounds) functioning as subject complements.
Swimming, cycling, and running are the three disciplines of a triathlon.
All three items are gerunds (-ing forms used as nouns).
The goals of the program are to educate the public, to raise awareness, and to promote healthy habits.
All three items are infinitive phrases.
The treasure was hidden under the old bridge, behind the stone wall, and beside the tall oak tree.
All three items are prepositional phrases with the same structure: preposition + article + adjective + noun.
The study found that exercise improves mood, that sleep enhances memory, and that nutrition affects concentration.
All three items are noun clauses beginning with "that."
Parallelism applies to pairs joined by and, but, or, nor, yet, and so -- not only to longer lists.
| Not Parallel | Parallel |
|---|---|
| She enjoys painting and to sculpt. | She enjoys painting and sculpting. |
| The plan is simple but has effectiveness. | The plan is simple but effective. |
| You can call me or sending an email. | You can call me or send an email. |
| He is not lazy nor does he lack intelligence. | He is neither lazy nor unintelligent. |
Whenever you join two elements with a conjunction, check that they match in form.
Here is a simple three-step process:
Find the conjunction or list. Look for and, or, but, nor, commas in a series, or correlative conjunctions (both/and, either/or, etc.).
Identify each element. What are the individual items being joined? Write them out separately.
Check the form. Are they all the same type (all nouns? all gerunds? all clauses?)? If not, revise the odd one out to match the others.
Example walkthrough:
Original: "The company values innovation, working collaboratively, and to deliver quality products."
Three different forms. Choose one pattern and apply it to all three:
Revised (nouns): "The company values innovation, collaboration, and quality."
Revised (gerunds): "The company values innovating, collaborating, and delivering quality products."
Wrong: "The job requires patience, being organized, and you need to communicate well."
Right: "The job requires patience, organization, and strong communication skills."
Wrong: "The researcher collected the samples and the data was analyzed."
Right: "The researcher collected the samples and analyzed the data."
Wrong: "She studied the material, reviews the notes, and will take the exam."
Right: "She studied the material, reviewed the notes, and took the exam."
| Principle | Example |
|---|---|
| Match nouns with nouns | courage, strength, and wisdom |
| Match verbs with verbs | plan, execute, and evaluate |
| Match adjectives with adjectives | fast, reliable, and affordable |
| Match gerunds with gerunds | reading, writing, and speaking |
| Match infinitives with infinitives | to learn, to grow, and to succeed |
| Match phrases with phrases | in the morning and in the evening |
| Match clauses with clauses | what you know and what you can do |
Parallelism is not just a grammar rule -- it is a writing strategy. Master it, and your sentences will be clearer, more elegant, and more convincing.
约8分钟阅读
Lists are everywhere in academic, professional, and exam writing. Whenever you present three or more items in a series, each item must follow the same grammatical pattern. This section covers the specific rules for maintaining parallelism in lists, series, and correlative conjunction pairs.
The simplest parallel list contains all nouns or noun phrases.
The survey measured satisfaction, engagement, and retention.
All three items are abstract nouns. Now consider a broken version:
The survey measured satisfaction, how engaged employees were, and retention.
The second item is a noun clause, not a noun. It breaks the pattern. Fix it:
The survey measured satisfaction, engagement, and retention.
When your list items are noun phrases (article/adjective + noun), keep the structure consistent:
The ideal candidate has strong analytical skills, excellent communication abilities, and relevant industry experience.
Each item follows the pattern: adjective + noun + noun. Compare the broken version:
The ideal candidate has strong analytical skills, communicates excellently, and relevant industry experience.
The second item switched to a verb phrase. This jars the reader and should be revised.
When listing actions, keep every verb in the same form.
Employees must arrive on time, complete all assigned tasks, and report any issues immediately.
The modal "must" governs all three verbs. Each is in the base form.
The team designed the prototype, tested it under real conditions, and presented the results to stakeholders.
Every morning, she checks her email, reviews her calendar, and plans her priorities for the day.
Wrong: "The committee reviewed the proposal, the committee discussed the budget, and voted on the timeline."
This breaks parallelism by inserting "the committee" before the second verb but not the third. Either include the subject before every verb or before none:
Right: "The committee reviewed the proposal, discussed the budget, and voted on the timeline."
Gerund lists are very common in writing about activities, processes, and interests.
The workshop focuses on developing critical thinking, improving research methods, and strengthening academic writing.
All three items are gerund phrases. A broken version:
The workshop focuses on developing critical thinking, to improve research methods, and the strengthening of academic writing.
This mixes a gerund, an infinitive, and a nominalized noun phrase. Pick one form and use it consistently.
Infinitive lists often appear after verbs like want, need, plan, hope, decide, and aim.
The organization aims to reduce carbon emissions, to promote renewable energy, and to educate the public about sustainability.
Both options are acceptable, but be consistent:
Repeated: The plan is to identify the problem, to develop solutions, and to implement changes.
Not repeated: The plan is to identify the problem, develop solutions, and implement changes.
If you repeat "to" before one item, repeat it before all items. If you omit it after the first, omit it for all subsequent items.
The new policy is fair, transparent, and enforceable.
All three are adjectives functioning as subject complements. A broken version:
The new policy is fair, has transparency, and can be enforced.
This mixes an adjective, a verb phrase, and a passive construction.
The files can be found in the main office, on the shared drive, or at the reception desk.
Each item is a prepositional phrase: preposition + article + noun. The pattern is clean and predictable.
When list items are full clauses, maintain the same clause structure.
The report concluded that costs had increased, that productivity had declined, and that employee morale had suffered.
All three are noun clauses introduced by "that." You could omit "that" after the first instance, but if you include it, include it for all:
Also correct: The report concluded that costs had increased, productivity had declined, and employee morale had suffered.
Correlative conjunctions are pairs of conjunctions that work together. The most common pairs are:
The critical rule: whatever grammatical structure follows the first conjunction must also follow the second.
| Not Parallel | Parallel |
|---|---|
| She is both intelligent and she works hard. | She is both intelligent and hardworking. |
| The policy both increases revenue and costs are reduced. | The policy both increases revenue and reduces costs. |
| Both the design is elegant and functional. | The design is both elegant and functional. |
After "both," we have an adjective ("intelligent"), so after "and," we need an adjective ("hardworking"), not a clause.
| Not Parallel | Parallel |
|---|---|
| You can either take the bus or a taxi is available. | You can either take the bus or call a taxi. |
| Either we leave now or to wait for the next train. | We can either leave now or wait for the next train. |
| She will either study medicine or going into law. | She will either study medicine or go into law. |
| Not Parallel | Parallel |
|---|---|
| He neither called nor did he send an email. | He neither called nor sent an email. |
| The solution is neither practical nor does it have efficiency. | The solution is neither practical nor efficient. |
| Neither the teacher nor students were ready. | Neither the teacher nor the students were ready. |
This pair is the trickiest because writers often misplace "not only."
| Not Parallel | Parallel |
|---|---|
| She not only speaks French but also German is spoken by her. | She speaks not only French but also German. |
| The project not only improved efficiency but also costs were reduced. | The project not only improved efficiency but also reduced costs. |
| Not only is the software expensive but also it is difficult to use. | The software is not only expensive but also difficult to use. |
The placement test: Take whatever follows "not only" and whatever follows "but also" and check if they are the same form:
You must decide whether to accept the offer or to negotiate better terms.
Both elements after the correlative conjunction are infinitive phrases.
Not parallel: You must decide whether to accept the offer or if negotiation is better.
This mixes an infinitive phrase with a clause.
The Oxford comma (the comma before "and" or "or" in a list of three or more items) does not affect parallelism, but it does improve clarity:
Without Oxford comma: "The course covers reading, writing and grammar."
With Oxford comma: "The course covers reading, writing, and grammar."
Both are grammatically correct, but the Oxford comma prevents ambiguity in complex lists:
"I admire my parents, Nelson Mandela and Marie Curie." (Are your parents Nelson Mandela and Marie Curie?)
"I admire my parents, Nelson Mandela, and Marie Curie." (Three separate items -- clear.)
Use the Oxford comma consistently in academic and professional writing.
Parallelism is equally important in bulleted and numbered lists. Each item should begin with the same grammatical form.
Not parallel:
Parallel (all imperative verbs):
Parallel (all noun phrases):
This principle applies to resume bullet points, presentation slides, reports, and any document with listed items.
Revise each sentence to make the list parallel. Suggested answers are below.
The manager is responsible for hiring staff, training, and to evaluate performance.
The study examined how students learn, teacher effectiveness, and whether technology helps.
Good leaders listen to their team, making decisions quickly, and inspire others.
The scholarship is available to students who are academically gifted, show financial need, or involved in community service.
The recipe calls for chopping the onions, the tomatoes should be diced, and mincing the garlic.
Suggested Answers:
The manager is responsible for hiring staff, training employees, and evaluating performance. (all gerund phrases)
The study examined student learning, teacher effectiveness, and technology's impact. (all noun phrases)
Good leaders listen to their team, make decisions quickly, and inspire others. (all present-tense verbs)
The scholarship is available to students who are academically gifted, financially disadvantaged, or active in community service. (all adjective phrases)
The recipe calls for chopping the onions, dicing the tomatoes, and mincing the garlic. (all gerund phrases)
| Pattern | Rule |
|---|---|
| Lists of 3+ items | All items must share the same grammatical form |
| Noun lists | All nouns or noun phrases |
| Verb lists | All same tense, same form |
| Gerund lists | All -ing forms |
| Infinitive lists | All to + verb; repeat or omit "to" consistently |
| Correlative conjunctions | What follows the first word must match what follows the second |
| Bullet points | Start every bullet with the same part of speech |
约7分钟阅读
Comparisons are one of the most frequent sources of faulty parallelism. Whenever you use than, as, like, compared to, or other comparison structures, the elements being compared must be in the same grammatical form. This section explains the rules, shows common errors, and provides before-after rewrites for practice.
When you compare two things, you are saying they are similar or different in some way. For the comparison to be logical and grammatically correct, the two things must be the same type of element.
Parallel: Running a marathon is harder than running a 5K.
Not parallel: Running a marathon is harder than when you run a 5K.
In the first sentence, you compare two gerund phrases (running a marathon vs. running a 5K). In the second, you compare a gerund phrase with a clause. The comparison is unbalanced.
"Than" is the most common comparison word, and it is where parallelism errors occur most often.
| Not Parallel | Parallel |
|---|---|
| The cost of living in Tokyo is higher than London. | The cost of living in Tokyo is higher than the cost of living in London. |
| His essay was more persuasive than the other students. | His essay was more persuasive than the other students' essays. |
| The population of India is larger than China. | The population of India is larger than that of China. |
In the first "not parallel" example, you are accidentally comparing "the cost of living" with "London" -- those are not the same type of thing. You are not comparing a cost with a city; you are comparing costs in two cities.
Pro tip: Use that of or those of to avoid awkward repetition:
The climate of Brazil is warmer than that of Canada. ("that" = "the climate")
The policies of this government differ from those of the previous administration. ("those" = "the policies")
| Not Parallel | Parallel |
|---|---|
| She prefers reading to when she watches TV. | She prefers reading to watching TV. |
| To invest in education is better than spending on luxuries. | Investing in education is better than spending on luxuries. |
| He would rather study at home than going to the library. | He would rather study at home than go to the library. |
With "would rather ... than," both verbs should be in the base form.
| Not Parallel | Parallel |
|---|---|
| The new model is more efficient than it is durable. | The new model is more efficient than durable. |
| Her approach was more practical and less based on theory. | Her approach was more practical and less theoretical. |
| Not Parallel | Parallel |
|---|---|
| What you say matters less than your actions. | What you say matters less than what you do. |
| How a company treats its employees is as important as their products. | How a company treats its employees is as important as how it develops its products. |
When one side of the comparison is a clause, the other side should also be a clause.
The "as ... as" structure compares two things that are equal (or not equal).
| Not Parallel | Parallel |
|---|---|
| Writing an essay is as challenging as to prepare for an exam. | Writing an essay is as challenging as preparing for an exam. |
| This project is as important as it will affect everyone. | This project is as important as the previous one. |
| She is as skilled at management as she communicates well. | She is as skilled at management as at communication. |
"Like" and "unlike" introduce comparisons that must also be parallel.
| Not Parallel | Parallel |
|---|---|
| Like running, when you swim it is good exercise. | Like running, swimming is good exercise. |
| Unlike the previous report, the researchers changed their methodology. | Unlike the previous report, this report uses a different methodology. |
| Like most students, the workload bothered her. | Like most students, she found the workload overwhelming. |
After "like" or "unlike," the element that follows the comma must be the thing actually being compared. In the third "not parallel" example, "the workload" is not being compared to "most students" -- she is.
| Not Parallel | Parallel |
|---|---|
| The new system's efficiency is impressive compared to the old system. | The new system's efficiency is impressive compared to the old system's efficiency. |
| Working from home has benefits compared to an office environment. | Working from home has benefits compared to working in an office. |
Make sure you compare the same type of thing: efficiency with efficiency, an activity with an activity.
Study these transformations carefully. Each "before" sentence contains a parallelism error in the comparison. The "after" version corrects it.
Before: "The salaries of nurses are lower than doctors."
Problem: Compares "salaries" with "doctors" -- salaries are not doctors.
After: "The salaries of nurses are lower than those of doctors."
Before: "Swimming in the ocean is more dangerous than a pool."
Problem: Compares the activity "swimming in the ocean" with the object "a pool."
After: "Swimming in the ocean is more dangerous than swimming in a pool."
Or more concisely: "Swimming in the ocean is more dangerous than in a pool."
Before: "The professor's lectures were more engaging than the textbook."
Problem: Compares "lectures" with "the textbook" -- two different types of thing.
After: "The professor's lectures were more engaging than the textbook's content."
Or: "The professor's lectures were more engaging than the readings in the textbook."
Before: "Learning a language through immersion is more effective than when you study from a book."
Problem: Compares a gerund phrase with a clause.
After: "Learning a language through immersion is more effective than studying from a book."
Before: "Unlike the first draft, she revised her argument completely in the second draft."
Problem: "Unlike the first draft" should compare to another draft, but the sentence subject is "she."
After: "Unlike the first draft, the second draft presented a completely revised argument."
Before: "To teach is as rewarding as learning new things."
Problem: Mixes infinitive ("to teach") with gerund ("learning").
After: "Teaching is as rewarding as learning new things."
Or: "To teach is as rewarding as to learn new things."
Before: "The impact of social media on politics has been greater than the economy."
Problem: Compares "the impact on politics" with "the economy" -- impact vs. economy.
After: "The impact of social media on politics has been greater than its impact on the economy."
Or: "The impact of social media on politics has been greater than on the economy."
Before: "She would rather write a research paper than giving a presentation."
Problem: After "would rather ... than," both verbs must be base form.
After: "She would rather write a research paper than give a presentation."
Some comparison errors go beyond grammar into logic. Even when the forms match, the comparison must make sense.
Wrong: "This city's traffic is worse than any city in the country."
This says the city's traffic is worse than any city -- including itself. Fix:
Right: "This city's traffic is worse than that of any other city in the country."
Ambiguous: "She likes chocolate more than her sister."
Does this mean "more than her sister likes chocolate" or "more than she likes her sister"? Clarify:
Clear: "She likes chocolate more than her sister does."
Or: "She likes chocolate more than she likes her sister."
Circle every "than," "as ... as," "like," "unlike," and "compared to" in your essay.
Identify what is on each side of the comparison word. Write them out separately.
Ask: Are these the same type of thing? Noun vs. noun? Gerund vs. gerund? Clause vs. clause?
If they don't match, revise. Use "that of" / "those of" to avoid repetition. Match gerunds with gerunds, infinitives with infinitives.
Read the comparison aloud. If it sounds awkward, the structure is probably not parallel.
| Comparison Type | Parallel Example |
|---|---|
| than (nouns) | The GDP of Japan is higher than that of France. |
| than (gerunds) | Running is harder than walking. |
| than (base form with "rather") | I would rather read than watch TV. |
| as ... as | Writing is as important as reading. |
| like / unlike | Like the first study, the second study found similar results. |
| compared to | Working remotely offers flexibility compared to working in an office. |
约6分钟阅读
This section is your go-to reference for checking parallelism in your writing. It consolidates every rule from the previous sections into a concise, actionable format. Use it as a self-editing guide after you draft an essay, report, or exam response.
After writing a draft, go through these seven checks in order. Each targets a specific type of parallelism error.
Find: Every list of three or more items joined by commas and a conjunction (and, or, but).
Test: Write out each item separately. Do they all share the same grammatical form?
| Form | Correct Example |
|---|---|
| All nouns | strength, agility, and endurance |
| All adjectives | clear, concise, and compelling |
| All gerunds | planning, organizing, and executing |
| All infinitives | to plan, to organize, and to execute |
| All verb phrases | reviewed the data, analyzed the trends, and reported the findings |
| All prepositional phrases | in the office, at the factory, and on the construction site |
| All clauses | that costs increased, that quality declined, and that deadlines were missed |
If they don't match: Choose the most natural form and revise all items to follow it.
Find: Every pair joined by and, but, or, nor, yet, or so.
Test: Are the two elements the same grammatical type?
| Wrong | Right |
|---|---|
| She is talented and works hard. (adj + clause) | She is talented and hardworking. (adj + adj) |
| He likes fishing but not to hunt. (gerund + infinitive) | He likes fishing but not hunting. (gerund + gerund) |
| Call me or you can send an email. (imperative + clause) | Call me or send an email. (imperative + imperative) |
Find: Every use of both...and, either...or, neither...nor, not only...but also, whether...or.
Test: Take what follows the first word and what follows the second word. Are they the same form?
| Correlative | Wrong | Right |
|---|---|---|
| both...and | Both she is smart and kind. | She is both smart and kind. |
| either...or | Either you come or staying home. | Either come or stay home. |
| neither...nor | Neither helpful nor does it have relevance. | Neither helpful nor relevant. |
| not only...but also | Not only is it expensive but also time. | It requires not only money but also time. |
| whether...or | Whether to go or if we should stay. | Whether to go or to stay. |
Placement tip for "not only...but also": Place "not only" directly before the first element and "but also" directly before the second. Both elements should be at the same level of the sentence.
Find: Every use of than, as...as, like, unlike, compared to/with, similar to, different from.
Test: Are the two things being compared the same type of element? Are you comparing logically equivalent things?
| Wrong | Right | Why |
|---|---|---|
| The cost of A is higher than B. | ...higher than that of B. | Compare cost with cost, not cost with B. |
| Running is better than to walk. | Running is better than walking. | Gerund with gerund. |
| Unlike the old model, they improved speed. | Unlike the old model, the new model has better speed. | Compare model with model. |
Find: Every sentence where multiple verbs share the same subject.
Test: Are all verbs in the same tense and voice?
| Wrong | Right |
|---|---|
| She designed the survey and is analyzing the results. | She designed the survey and analyzed the results. |
| The data was collected and we analyzed it. | The data was collected and analyzed. (OR: We collected and analyzed the data.) |
| He runs the department, managed the budget, and will oversee the expansion. | He runs the department, manages the budget, and oversees the expansion. |
Exception: Tense shifts are acceptable when describing events at genuinely different times: "She studied medicine in London and now practices in New York." The tense change reflects a real change in time.
Find: Every bulleted or numbered list in your document.
Test: Does every item begin with the same part of speech?
Common patterns for bullet points:
| Pattern | Example |
|---|---|
| Imperative verbs | Review the document. Submit the form. Contact the office. |
| Gerunds | Reviewing documents. Submitting forms. Contacting offices. |
| Noun phrases | Document review. Form submission. Office contact. |
| Full sentences | The document must be reviewed. The form must be submitted. |
Choose one pattern and apply it to every item.
Find: All headings at the same level in your document.
Test: Do they follow the same pattern?
| Not Parallel | Parallel |
|---|---|
| "Introduction" / "Analyzing the Data" / "What We Concluded" | "Introduction" / "Analysis" / "Conclusion" |
| "How to Plan" / "Execution" / "Review Process" | "Planning" / "Execution" / "Review" |
This table lists the most frequent parallelism errors and their fixes. Use it as a rapid reference.
| Error Type | Example of Error | Fix |
|---|---|---|
| Mixed list forms | reading, to write, and math | reading, writing, and studying math |
| Gerund/infinitive mix | She likes to swim and running. | She likes swimming and running. |
| Missing parallel noun | The price of A is higher than B. | ...higher than that of B. |
| Correlative misplacement | Both she is smart and kind. | She is both smart and kind. |
| Active/passive mix | She wrote the intro and the conclusion was edited. | She wrote the intro and edited the conclusion. |
| Tense shift in list | He planned, is executing, and will review. | He planned, executed, and reviewed. |
| Unequal comparison | Working from home is better than an office. | Working from home is better than working in an office. |
| Bullet point inconsistency | Analyze data / The report / Writing conclusions | Analyze data / Review the report / Write conclusions |
| Subject insertion | She planned the event, she organized logistics, and managed the team. | She planned the event, organized logistics, and managed the team. |
| Article inconsistency | the manager, a director, and employees | the manager, the director, and the employees |
Follow this workflow to systematically eliminate parallelism errors from your writing.
Go through your draft and highlight or underline every and, or, but, nor, both, either, neither, not only, than, as, like, and unlike.
For each highlighted word, write out the elements it connects. Put them side by side:
"The program helps students improve their writing skills and to become better readers."
These do not match.
Decide which form works best in context. Usually, the simpler form wins:
Revised: "The program helps students improve their writing skills and reading abilities."
Or: "The program helps students improve their writing and become better readers."
Read the revised sentence aloud. Parallel sentences have a natural rhythm -- you can almost feel the balance. If a sentence feels lopsided, check the structure again.
Review all bullet points, numbered lists, and outline items. Apply the same process: highlight, identify, match, revise.
Here are all the parallelism rules in one place.
Items in a list must share the same grammatical form. All nouns, all gerunds, all infinitives, all adjectives, all clauses, etc.
Pairs joined by coordinating conjunctions must match. What comes before "and" must be the same form as what comes after.
Correlative conjunctions require parallel elements. The structure after the first word must mirror the structure after the second word.
Comparisons must compare equivalent things. Noun with noun, gerund with gerund, clause with clause. Use "that of" / "those of" to avoid false comparisons.
Verbs sharing a subject should be in the same tense and voice unless a genuine time shift justifies the change.
Bullet points and numbered lists must start with the same part of speech. Pick one pattern and use it for all items.
Headings at the same level should follow the same pattern. All nouns, all gerunds, all questions -- pick one.
When repeating function words (to, a, the, in, that), be consistent. Either repeat them before every item or omit them after the first.
Find and fix the parallelism errors in each sentence. Answers below.
The course teaches students to think critically, effective writing, and how to present their ideas.
Not only the project was expensive but also it took a long time.
The test scores of Group A were significantly higher than Group B.
She is responsible for managing the budget, coordinating events, and she trains new staff.
The report was thorough, well-researched, and it presented the data clearly.
Answers:
The course teaches students to think critically, to write effectively, and to present their ideas. (all infinitive phrases)
The project was not only expensive but also time-consuming. (adjective + adjective after correlative pair)
The test scores of Group A were significantly higher than those of Group B. (compare scores with scores)
She is responsible for managing the budget, coordinating events, and training new staff. (all gerund phrases)
The report was thorough, well-researched, and clearly presented. (all adjective/participial phrases)
Strict parallelism is the default for academic and professional writing. However, experienced writers sometimes break parallelism deliberately for rhetorical effect:
"He was my friend, my confidant, and the only person who ever truly understood me."
The third item is intentionally longer and more complex, creating emphasis. This is a stylistic choice, not an error.
The key distinction: know the rule before you break it. In exam writing, always maintain strict parallelism. In creative or persuasive writing, you may choose to vary the pattern for effect -- but only if the reader can tell it is intentional.
Parallelism is about creating patterns. Readers expect patterns to continue once they start. When you break a pattern by accident, the reader stumbles. When you maintain it, your writing flows smoothly, sounds confident, and scores well.
Make the seven-check process a habit: lists, pairs, correlatives, comparisons, verbs, bullet points, headings. Within a few weeks of deliberate practice, parallel structure will become automatic.
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