English

What Is Parallel Structure?

Items joined by and, or or a paired conjunction must share one grammatical form. One faulty sentence, three ways to repair it, and the pairs that force it.

Parallel structure

Parallel structure is the rule that words or phrases joined by and, or, or a paired conjunction must arrive in the same grammatical form as one another.

Also called: Parallelism, Parallel construction
Where students meet it: Grade 8 English, in the strand on sentence accuracy, and again in GCSE and IGCSE English Language writing, where the assessment objective on vocabulary and sentence structure rewards controlled sentences and penalises ones that change shape halfway through.

The short answer
Parallel structure means that items joined in a list, a comparison or a pair share the same grammatical form: all nouns, all -ing verbs, or all infinitives. 'I like reading, swimming and cycling' is parallel; 'I like reading, to swim and cycling' is not.

An example

Faulty: I like reading, to swim and I play cricket.

Three things are joined by and, and all three arrive in a different grammatical shape: a gerund, an infinitive, then a whole clause. The repair is to pick one shape and hold it. All gerunds gives 'I like reading, swimming and playing cricket'. All infinitives gives 'I like to read, to swim and to play cricket'. All clauses gives 'I read, I swim and I play cricket', which needs the sentence rebuilt around it but is sometimes the clearest of the three. Notice that none of the three repairs adds a single piece of information. They only stop the sentence changing gear.

Lists, pairs, comparisons: where the rule applies

Parallelism is not a rule about whole sentences. It applies at the exact points where a sentence joins two or more things together and asks the reader to hold them side by side — a list separated by commas, a pair joined by and or or, a comparison built on than or as, and a run of bullet points or headings.

At those joints the reader is already doing work, because they have to keep the opening of the sentence in mind while several endings arrive. Matching the grammatical shape removes the only avoidable part of that work. When the shapes do not match, the reader has to re-parse the sentence from the beginning to see where each item attaches, and that is why a non-parallel list reads as clumsy even to someone who could not name what is wrong with it.

The conjunctions that come in pairs

Some conjunctions arrive in two halves, and the two halves make a promise: whatever grammatical unit follows the first half will be matched by the unit following the second. These are the ones that catch people out most often, because the first half is usually placed too early in the sentence.

The test is mechanical. Cover everything except the words following each half of the pair and see whether the two pieces could swap places without breaking the sentence. 'She not only writes poetry but also the violin' fails: writes poetry is a verb phrase, the violin is a noun phrase, and they cannot swap. Moving the first half one word to the right fixes it — 'She writes not only poetry but also fiction' — or extending the second half does: 'She not only writes poetry but also plays the violin.'

not only ... but also
either ... or
neither ... nor
both ... and
whether ... or
not ... but

Why it shows up in marked writing

In an exam answer the damage is rarely a lost mark for grammar on its own. It is that a non-parallel list makes a confident sentence sound uncertain, and marks for structure and control are awarded on how the writing sounds as much as on whether it can be diagnosed as wrong.

The place it is most visible is a set of bullet points or subheadings, where the mismatch sits in a vertical column and the reader sees all the items at once. If one heading starts with a verb and the next with a noun, nothing has to be re-read for the fault to register.

Common questions

What is a simple example of parallel structure?

'The course teaches students to read closely, to argue clearly and to write quickly.' All three items are infinitives, so the opening of the sentence attaches cleanly to each of them. Change the third to 'and quick writing' and the sentence still makes sense, but the reader has to work out where the new item attaches.

Is parallel structure a grammar rule or a style rule?

Something between the two. A non-parallel list is not ungrammatical in the way a missing verb is ungrammatical — the meaning usually survives. But it is marked as an error by teachers and examiners in almost every system, because the fix is always available and the alternative reads as carelessness rather than as a choice.

Where should 'not only' go in a sentence?

Immediately before the first thing being contrasted, not earlier. If the second half is 'but also plays the violin', then 'not only' belongs before 'writes poetry'. If the second half is 'but also fiction', it belongs before 'poetry'. Deciding the second half first is usually the quickest way to place the first.

Does parallel structure apply to bullet points and headings?

Yes, and more visibly than anywhere else, because the items sit in a column where the reader takes them in together. Choose one opening form for the whole list — all verbs, all noun phrases, all full sentences — and keep it. Mixed forms in a list of headings are noticed immediately, even by readers who never think about grammar.

Sources

GCSE English Language (8700) — AQA

Last updated August 21, 2026