Grammar by Diagram is a book designed for anyone who wishes to improve grammatical understanding and skill. Using traditional sentence diagraming as a visual tool, the book explains how to expand ten basic patterns for simple sentences into compound, complex, and compound-complex sentences, and how to employ verbals (infinitives, gerunds, and participles), other specialized structures, and even punctuation for additional versatility.

The third edition includes more exercises at the foundational level and more focus on how to arrange and combine sentences for maximum effect. It also includes a new initial chapter on “preliminaries” to define a few basic but overarching concepts, a separate chapter on pronouns, and a chapter devoted to the connection between understanding grammar and writing effective sentences.