This document provides an introduction to principal word classes in grammar, including verbs, nouns, adjectives, adverbs, prepositions, pronouns, and determiners. It defines each word class and provides examples. Verbs denote actions or states of being. Nouns name things, people, places, or emotions. Adjectives modify nouns by describing. Adverbs modify verbs by describing how the action is done. Prepositions denote relationships between objects. Pronouns replace nouns. Determiners specify particular nouns.