This document is a guide for sentence correction on the GMAT. It provides an overview of English grammar concepts important for sentence correction, including parts of speech like nouns, pronouns, adjectives, adverbs and their usage. It also covers topics like subject-verb agreement, pronoun reference and cases, collective nouns, and distinguishing between adjectives and adverbs. The guide is intended to help review grammar rules and common errors tested on the GMAT sentence correction section.