In this paper we address the obfuscation surrounding the concept of learning communities by operationalizing "community" according to four characteristics that serve as boundaries for defining a community: access, relationships, vision, and function. Although these community boundaries sometimes overlap, they represent distinctive features of possible community structures. In addition to defining and discussing learning community boundaries, we share insights for researching learning communities. We believe a clearer understanding of how to define learning communities can assist scholars and practitioners in cultivating and studying these communities.