Many psychological scientists and behavioral neuroscientists affirm that “emotion” influences thinking, decision-making, actions, social relationships, well-being, and physical and mental health. Yet there is no consensus on a definition of the word “emotion,” and the present data suggest that it cannot be defined as a unitary concept. Theorists and researchers attribute quite different yet heuristic meanings to “emotion.” They show considerable agreement about emotion activation, functions, and regulation. The central goal of this article is to alert researchers, students, and other (...) consumers of “emotion” research to the multiple meanings or aspects that distinguished scientists attribute to ”emotion,” increase appreciation of its interesting and challenging complexity, and sharpen perspectives on “emotion” and the associated body of literature that is of critical significance to science and society. (shrink)