This document discusses morphology, which is the study of meaningful units in language. It defines morphology and describes the key concepts of morphemes, which are the smallest units of meaning, and how they are combined to form words. Specifically, it discusses free morphemes, which can stand alone as words, and bound morphemes, or affixes, which must be attached to other morphemes. It provides examples of prefixes, suffixes, and allomorphs, which are variants of morphemes. The document also lists and defines the nine main classes of words in English: nouns, determiners, pronouns, adjectives, verbs, adverbs, prepositions, conjunctions, and exclam