This commentary is a response to both Merkebu et al., (2024) and Ellaway and Patocka (2024) on the place and importance of definitions of key notions in health professions education (HPE). The author argues that definitions of key notions in HPE research, teaching, and assessment are both variably possible and variably useful. By differentiating across concepts, constructs, measures, and metrics, the author contextualizes the variable utility and necessity of definitions according to their intended use. While many conceptualizations of key notions peacefully co-exist in the current HPE literature, conflation across concepts, constructs, measures, and metrics lead to a fragmented literature base and problematic assumptions, operationalizations, and misattributions of some of our most closely held concepts.