This document discusses tree diagrams, which provide a visual representation of the grammatical structure of sentences. Tree diagrams show the hierarchical relationship between constituents in a sentence, with the largest units like clauses at the top and smaller units like words at the bottom. The document provides examples of different types of clauses and phrases that make up sentences and can be represented in tree diagrams, such as noun phrases, verb phrases, and prepositional phrases. Examples of tree diagrams are given to illustrate how they show the grammatical relationships between various constituents in sentences.