The document discusses the structure of words and their components. It explains that words are made up of smaller units called morphemes, which include root words and affixes. Root words are the core meaning of a word, and affixes like prefixes and suffixes can be added to root words to change the word's meaning or grammatical function. Morphemes can be either free morphemes that can stand alone as words, or bound morphemes that must be attached to other morphemes. The document also discusses the different lexical categories of words and how words are categorized based on their meaning and use.