This document discusses the language of interaction between people and the products/interfaces they use. It argues that we can gain insight by studying common interactions and the objects around us. Successful designs inherit meaning from other interfaces and use elements like colors, shapes, words and gestures that people are already familiar with. Over time, these elements and their meanings can evolve as they spread across different domains and products. The document provides various examples of how design principles like zoning, priority, clarity and perspective impact user interactions and understanding.