The collection of articles presented by Pollak, Camras, and Cole (2019) provides a stimulating survey of the current state of research on emotional development. However, the special issue also makes apparent the need for defining the construct of interest. Definitions of emotions guide how researchers deal with fundamental theoretical and methodological issues in emotion research. In this commentary, we contrast 2 views of emotion: the structuralist and functionalist perspectives. We illustrate the consequences of each view for the design and interpretation of empirical research and highlight benefits of adopting a functionalist perspective on emotional development.