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Parallelism (grammar) In grammar, parallelism, also known as parallel structure or parallel construction, is a balance within one or more sentences of similar phrases or clauses that have the same grammatical structure. The application of parallelism improves writing style and readability, and is thought to make sentences easier to process.
Here is an example of parallel structure paired with a non-parallel construction. On his day off, he did this, this and did that. On his day off, he did this, this and that. Joel packed sneakers, sweatpants and put in three pairs of socks. Joel packed sneakers, sweatpants and three pairs of socks.