Grammatical parallelism, also known as parallel structure or parallel construction, refers to the use of a consistent grammatical form for items in a series, list, or comparison. In parallel structure, the elements in a sentence that have the same function and importance are structured in a similar way, using the same grammatical form.
Here is an example of a sentence that does not use parallel structure:
"Not only did she enjoy playing the piano, but also singing in the choir."
In this example, the structure of the sentence is not parallel because the verb tense changes between "enjoy playing" and "singing."
Here is an example of the same sentence using parallel structure:
"Not only did she enjoy playing the piano, but also singing in the choir."
In this example, the structure of the sentence is parallel because both elements of the comparison use the same grammatical structure, with the verb "enjoy" followed by the gerund "playing" and "singing."
Parallel structure helps to create balance and clarity in writing and makes it easier for the reader to follow the writer's train of thought