ACT® · English: Sentence Structure and Formation
Parallelism in Complex Series and Correlative Pairs
When items are joined by pairs like "not only...but also" or strung into a series, every item must share the same grammatical form. One mismatched piece breaks the sentence even if the meaning is clear.
Parallelism means that items doing the same job in a sentence share the same grammatical shape. 'Not only quick but also she is precise' fails because 'quick' is an adjective and 'she is precise' is a whole clause. They are not doing the same job in the same way, so the sentence feels lopsided even though you understand it. 'Not only quick but also precise' fixes this by making both halves plain adjectives.
Correlative pairs such as not only/but also, either/or, neither/nor, and both/and work like a template. Whatever grammatical form follows the first half must be echoed exactly after the second half. If 'either' is followed by a verb, 'or' must also be followed by a verb; if 'both' is followed by a noun, 'and' must be followed by a noun. This is why placement matters: in 'both she sang and danced,' 'both' sits before a clause (she sang) but 'and' is followed by just a verb (danced). Moving 'both' to sit after 'she' — 'she both sang and danced' — lines up two verbs correctly.
The same rule scales up to longer series, including series of full clauses or participles. 'The plan was praised by critics, adopted by cities, and it saved money' breaks because the first two items are past participles (praised, adopted) describing the plan, while the third switches to a new subject and verb. Fixing it means finishing the list in the same participle form. This topic sits next to modifier placement and verb tense consistency, because all three ask the same underlying question: does every piece of the sentence match the grammatical pattern the rest of the sentence has already set up?
Key terms
- Parallelism
- The rule that items sharing a grammatical role in a sentence must share the same grammatical form.
- Correlative pair
- A two-part connector such as either/or or not only/but also that links matching elements.
- Participle
- A verb form, often ending in -ed or -ing, used as an adjective, as in 'praised' or 'adopted.'
- Infinitive
- The base form of a verb preceded by 'to,' such as 'to quit.'
Watch it explained
- How it worksHow do correlative pairs such as 'not only, but also' force whatever follows each half to match in form?
- Worked exampleWalk me through fixing 'She either wanted a raise or to quit' so both halves of the pair match.
- Worked exampleFind the break in 'The plan was praised by critics, adopted by cities, and it saved money.'
- Common mistakeWhy isn't 'both' free to sit anywhere it likes, as in 'both she sang and danced'?
- Going furtherWhat happens to parallel structure when the items in a series are full clauses rather than phrases?
Check yourself
End of topic.