Quite diverse in their foci and specific themes, the seven articles collected in this special issue are unified by their common conceptual framework. Grounded in the premise that thinking can be usefully defined as self-communicating and that mathematics can thus be viewed as a discourse, the communicational framework provides a unified set of conceptual tools with which to investigate cognitive, affective and social aspects of mathematics learning. The communicational tools are employed by the authors as they investigate diverse aspects of mathematical discourse and explore its development in the classroom and beyond. The seven studies combine together to produce a set of insights, some of which go against widespread beliefs about teaching and learning mathematics.