place in the set of concepts considered enactivist in this issue.The words 'enaction' and 'enactive' are used first by Varela, Thompson and Rosch (1991) to describe the nonrepresentationalist view of cognition they set out, cognition as "embodied action".Let us explain what we mean by this phrase embodied action. By using the term embodied we mean to highlight two points: first, that cognition depends upon the kinds of experience that come from having a body with various sensorimotor capacities, and second, that these individual sensorimotor capacities are themselves embedded in a more encompassing biological, psychological, and cultural context. By using the term action we mean to emphasize once again that sensory and motor processes, perception and action, are fundamentally inseparable in lived cognition. Indeed, the two are not merely contingently linked in individuals; they have also evolved together. We can now give a preliminary formulation of what we mean by enaction. In a nutshell, the enactive approach consists of two points: (1) perception consists in perceptually guided action and (2) cognitive structures emerge from the recurrent sensorimotor patterns that enable action to be perceptually guided (Varela et al. 1991, pp. 172-173).Below we will unpack the concepts of embodiment, perceptually guided action, and recurrent sensorimotor patterns, used here to describe enaction. First, however, we will briefly discuss how the concept of enaction is related to other 'enactivist' concepts, especially its origins in the work of Maturana and Varela.The Embodied Mind (Varela et al. 1991) was written over a period of time in the late 1980s. It incorporates a Abstract This article discusses key concepts within enactivist writing, focussing especially on concepts involved in the enactivist description of cognition as embodied action: perceptually guided action, embodiment, and structural coupling through recurrent sensorimotor patterns. Other concepts on which these concepts depend are also discussed, including structural determinism, operational closure, autonomy, autopoiesis, consensual domains, and cognition as effective action. Some related concepts that follow from an enactivist view of cognition are considered, in particular bringing forth a world and languaging. The use of enactivism as a methodology in mathematics education is also outlined. References to mathematics education research reported in this issue and elsewhere are used throughout to provide illustrations.