Third-degree price discrimination is taught in almost every intermediate microeconomics class. The theory, geometry, and the algebra behind the concept are simple, and the phenomenon is commonly associated with the sale of many of the goods and services used frequently by students. Classroom discussion is usually vibrant as students can relate their experiences of being on the receiving end of third-degree price discrimination, usually to their advantage. However, the precision of the language used in the exposition of the theory in textbooks is generally less precise than one would hope for, leading students to confuse slope and elasticity. The authors ask textbook writers to provide greater precision in their explanation of why differing elasticities are associated with the prices paid by two (or more) distinct groups of buyers facing third-degree price discrimination.