1. What parallel structure means
Parallel structure presents elements of equal importance consistently. For example, expanding, hiring and extending form a clear list after recommends. The forms must fit the construction they share. This is not a general ban on coordinating different kinds of phrases: She is friendly and in charge is possible.
This rule operates within ONE sentence. It concerns the form of items in a list or comparison, rather than connections between sentences or paragraphs.
X, Y, and Z → use matching forms for a clear parallel list: nouns / gerunds / infinitives / clauses.
The proposal recommends expanding the library, hiring two tutors, and extending opening hours.
The proposal recommends expanding the library, hiring two tutors, and extending opening hours.
Expanding, hiring and extending are three gerunds sharing recommends. All three have the same form.
A good mentor listens carefully, gives honest feedback, and follows up regularly.
A good mentor listens carefully, gives honest feedback, and follows up regularly.
Listens, gives and follows up are three present simple verbs sharing one subject; all three maintain the same form.
2. The shared introductory element
When one verb, preposition or auxiliary introduces a list, every item should fit grammatically if it is used on its own in place of the whole list.
A simple check is to read the shared word with each item separately. If one combination does not fit naturally, check and repair its form.
verb / preposition + [item 1, item 2, and item 3] → substitute each item individually for the bracketed list.
- verb / V —
- A word for an action or state, such as work or be. The pattern determines its form.
- preposition —
- A word showing a relationship, such as in, on or from: from Ukraine.
The lab requires students to label samples, record temperatures, and log results every hour.
The lab requires students to label samples, record temperatures, and log results every hour.
The shared to introduces three base verbs: to label, (to) record and (to) log.
She is responsible for scheduling meetings, drafting minutes, and archiving decisions.
She is responsible for scheduling meetings, drafting minutes, and archiving decisions.
The preposition for introduces three gerunds. Each item works on its own: responsible for scheduling / for drafting / for archiving.
3. Paired, or correlative, conjunctions
Not only...but also, either...or, neither...nor and both...and introduce pairs of elements. Matching grammatical forms provide a clear parallel pattern for these pairs.
For clarity, place the two halves of the pair before the elements you want to contrast: not only to cut waste but also to save money. Matching structures make the focus clear. More complex combinations are also possible when each part is grammatically complete.
not only + [form A] but also + [the same form] / either + [form A] or + [the same form]
The policy is designed not only to cut waste but also to save money.
The policy is designed not only to cut waste but also to save money.
The elements after not only and but also are both infinitives: to cut and to save.
The committee will either postpone the vote or reschedule the meeting entirely.
The committee will either postpone the vote or reschedule the meeting entirely.
The elements after either and or are both base verbs, postpone and reschedule, sharing will.
4. Parallelism in comparisons
A comparison should relate corresponding actions or qualities. Matching forms are often the easiest option: Reviewing… is more useful than rushing… However, the second part may be a full or reduced clause, so the two sides do not always have identical surface forms.
A common mismatch is to begin a direct comparison of actions with a gerund and finish it with an infinitive, or the reverse. Check whether both parts fit the chosen comparison pattern.
action or quality being compared + than / as + corresponding action, quality or comparative clause
- clause —
- A construction with a verb, often with its own subject: when I arrived. A non-finite clause may leave the subject unspoken: to get home.
Reviewing the draft carefully is more useful than rushing to submit it.
Reviewing the draft carefully is more useful than rushing to submit it.
Both sides of the comparison use gerunds: reviewing and rushing.
The new intern writes as clearly as she speaks.
The new intern writes as clearly as she speaks.
Clearly is an adverb modifying writes; the clause she speaks follows the second as. The meaning compares the clarity of the intern’s writing and speech.
5. Common breaks in the pattern
Common problems include mixing base verbs, -ing forms and to-infinitives in one list, or combining a short phrase with a full clause that has its own subject where the shared construction does not support that mixture.
The final item is particularly likely to drift out of the chosen pattern: it is often added as a separate thought after the first two have already been written.
The training helps new hires understand policies, build confidence, and manage time effectively.
The training helps new hires understand policies, build confidence, and manage time effectively.
The three base verbs after helps... (to) are understand, build and manage. None changes form, including the last one.
The article discusses causes, consequences, and possible solutions.
The article discusses causes, consequences, and possible solutions.
Three nouns in a row provide a simple way to avoid mixing forms.
6. When different forms are natural
Not every three-item list needs detailed analysis. The items may differ in length as long as their grammatical role remains the same—for example, they may all be adjective phrases even if one is longer than the others.
Two elements joined by a simple and form an ordinary, everyday construction. They become a particular learning focus here when their forms actually diverge.
This rule does not cover reference words such as this, that and such for connecting to an earlier sentence, or discourse markers such as however and in addition between paragraphs. Those are neighbouring rules in this topic. It also does not cover list punctuation, such as the comma before and.
The report is accurate, well-organized, and easy to follow.
The report is accurate, well-organized, and easy to follow.
Well-organized and easy to follow are adjective phrases of different lengths, but both serve an adjectival role. Different lengths do not break parallel structure.
Managers should praise good work and address problems quickly.
Managers should praise good work and address problems quickly.
The two verbs share should and already form a parallel pair. Parallelism does not require a list of three items.
7. Applying the rule: checking your writing
For a practical check, find the shared word before the list, separate out the items, and read the shared word with each item individually.
If the pattern is broken, repair the item that does not fit the others rather than rewriting the entire sentence.
In formal academic writing, parallel form is particularly noticeable in concluding sentences and bullet points. It signals careful organization to the reader.
Find the list → identify the first item’s form → check each remaining item → repair the item that does not fit.
Before submitting the report, check that every heading uses the same tense, every bullet starts with a verb, and every claim has a source.
Before submitting the report, check that every heading uses the same tense, every bullet starts with a verb, and every claim has a source.
The three clauses each follow every + noun + verb. The checking advice is itself written in parallel form.
A strong summary states the problem, outlines the method, and highlights the result.
A strong summary states the problem, outlines the method, and highlights the result.
Three present simple verbs share the subject summary, a typical structure in an academic summary.
Common mistakes
Incorrect:The manual explains how to install the software, updating the drivers, and to run the diagnostics.
Correct:The manual explains how to install the software, update the drivers, and run the diagnostics.
After how to, install, update and run make the clearest sequence here. To can also be repeated before each item; repetition itself is not an error. Updating breaks the chosen infinitive pattern.
Incorrect:The workshop covers writing clear emails, giving feedback, and to running meetings.
Correct:The workshop covers writing clear emails, giving feedback, and running meetings.
To running does not fit this list after covers. Running makes the list parallel. How to run meetings could also be a grammatical complement, although it would give that item a different form.
Incorrect:The award recognises employees who mentor juniors, who improve processes, and contributing to the community.
Correct:The award recognises employees who mentor juniors, who improve processes, and who contribute to the community.
The three relative clauses in this pattern use the same opening, who + verb. Contributing does not fit that sequence.