Recognizing that all traits are the result of an interaction between genes and environment, I offer a set of criteria for nevertheless making sense of our practice of singling out certain traits as genetic ones, in effect making a distinction between causes and mere conditions. The central criterion is that a trait is genetic if it is genetic differences that make the differences in that trait variable in a given population. A second criterion requires that genetic traits be individuated in (...) a way that matches what some genetic factors cause specifically. Clarifying our causal and classificatory language here can help us to avoid confusions of both theoretical and practical significance. (shrink)