This document discusses the grammar concept of parallelism. Parallelism refers to using similar grammatical structures in a sentence to emphasize equivalent ideas or items in a list or series. It makes writing more concise, clear and readable. The document provides examples of proper parallel structure with word series, prepositional phrases, clauses, infinitives, correlative conjunctions like "either/or" and "neither/nor", and words ending in "-ing". Parallel structure should be used consistently within a sentence or list.