The document discusses how prefixes and suffixes can change the meaning or function of words. It provides examples of how suffixes like -ity, -ence/-ance, -ize, -en, and -fy can modify nouns and verbs. It also explains how prefixes like un- can alter the meaning of words. Suffixes like -ful and -less are used to modify adjectives, while -ly suffixes modify adverbs.