We review research literature concerning "number sense" from several related fields. Whereas other authors have pointed to difficulty defining "number sense" or to some degree of inconsistency in the literature, we argue instead that this is a case of polysemy: There are 3 different constructs that go by the same name. In this article, we clarify the research literature concerning "number sense" by naming and defining these 3 constructs, identifying similarities and differences between them, and contrasting themes in each body of literature by drawing upon a sample of 124 research articles that focus on "number sense." [For complete proceedings, see ED581294.]