Concepts and conceptions are of central interest to mathematics educators, and there appears to be hardly an article in the literature that does not contain multiple uses of one or the other term.1 There are also continued efforts to come to grips with the nature of mathematical conceptions, which have been theorized, for example, in the form of a (complementarity) duality of mathematical processes and products; a three-world hypothesis including embodied, proceptual (procedural and conceptual), and formals worlds; and the dialectics of concept and concept defi nition.