Morphology, or the study of words, how words are formed, and the relationship between words and their parts, allows students to understand how words change in order to expand their own vocabulary and communicate effectively. In the English language, the information that a word conveys can be changed by adding other word parts to it. A word can change in meaning or function by adding these word parts. For example, the word happy changes in meaning when the prefix un- is added to create unhappy.

Over time, students must understand how the letters in a language create sounds and how those sounds together create a word. For students to be able to speak, read, or write in a language, they must first understand how the words in that language are constructed so they can read and/or spell them on their own. Without this understanding, students cannot combine words to create sentences that convey ideas, which is the goal of communication.