From charts, texts, and graphs to illustrations, icons, and screens, we live in an information age saturated with visual language. Yet the underlying principles that provide structure for visual language have long eluded scholars of rhetoric, design, and engineering. To function as a language that reliably conveys meaning, visual language must embody codes that normalize its practices among both the designers who employ it and the readers who interpret it.

In this wide-ranging analysis, Charles Kostelnick and Michael Hassett demonstrate how visual language in professional...