What parallel structure means
Parallel structure (parallelism) means that items doing the same job in a sentence take the same grammatical form. In a list, every item should match: «She likes swimming, running, and hiking.» When one item changes form — «swimming, to run, and hiking» — the reader has to re-read the sentence at the odd item, and the writing feels uneven even when every word is correct.
The same rule applies to paired phrases joined by both … and, either … or, neither … nor and not only … but also.
The mismatches this checker looks for
The checker reads the form of each item from its first word and compares them. It reports a sentence when two or more items have a recognisable form and the forms disagree:
- -ing and to + verb in one list: «He enjoys reading, to write, and painting.»
- Mixed forms in a pair: «She is not only learning English but also to teach it.»
Plain noun lists such as «apples, oranges, and bananas» are not flagged: there is no verbal form to compare. A list of prepositional phrases is only compared with another prepositional phrase.
How to fix faulty parallelism
Pick one form and apply it to every item. There are usually two correct versions:
- Before: «My hobbies are reading, to write, and painting.»
All -ing: «My hobbies are reading, writing, and painting.» - Before: «She wants to travel, studying abroad, and to learn two languages.»
All to + verb: «She wants to travel, to study abroad, and to learn two languages.»
For a pair, match the second part to the first: «not only learning English but also teaching it.» Choose the form that reads best with the verb before the list.
What this checker cannot see
This tool uses browser-based rules, not a full grammatical parser. It does not catch every parallelism error. In particular it does not compare adjectives with noun phrases («smart and a hard worker»), clauses with phrases, or verb tenses inside a list. A sentence with no flag is not a guarantee of parallel structure; read each list once aloud.
Take it further with Diglot
This free tool runs in your browser. When you want to act on what it shows — fix the grammar, tighten the phrasing, or make your English read like a native wrote it — that is what Diglot is built for. The free tier is meaningful for daily writing, no card required.
Frequently asked questions
- What is parallel structure?
- Parallel structure means that items with the same function in a sentence use the same grammatical form. In a list, that means every item is an -ing form, or every item is a to + verb form, or every item is a noun phrase. Matching forms make a sentence easier to read.
- What is an example of faulty parallelism?
- «She likes swimming, to run, and hiking» mixes -ing forms with a to + verb form. Make the items match: «She likes swimming, running, and hiking.» The same applies to pairs: «not only learning English but also to teach it» becomes «not only learning English but also teaching it».
- Does a parallel structure checker find every error?
- No. This checker compares the form of list items and paired phrases that it can read from the first word of each item: -ing forms, to + verb and prepositional phrases. It does not compare adjectives with noun phrases, or clauses with phrases. Read your lists aloud as well.
- Do items in a list always have to be -ing forms?
- No. Any single form works as long as the items match. A list of noun phrases, a list of to + verb forms or a list of -ing forms are all parallel. The error is switching between forms inside one list.
- Is my text uploaded or stored anywhere?
- No. The parallel structure checker runs 100% in your browser using client-side JavaScript. Your text is private and never leaves your device.
