This contribution draws on an international Lexicon project that set out to document the professional language employed in nine countries (Australia, Chile, China, the Czech Republic, Finland, France, Germany, Japan and the USA) for the description of middle school mathematics classrooms. The initial interest is lexical and concerns the actual terms by which students, teachers and researchers name the objects in their respective worlds.
Documentation of the content and structure of classroom-related lexicons in nine countries reveals patterns of connection in the pedagogical terminology in each country, as well as the practical enactment of cultural-historical differences encrypted in the terms by which classroom phenomena are named and from which each community constructs its instruction and its theory. Comparison of the lexicons of Australian and Czech Republic middle school mathematics teachers indicates the variation possible within two Western teaching communities with different pedagogical traditions.