Our presentation focuses on the development process of the current German lexicon and its integration into teacher education in Bremen. As language itself is permanently undergoing change (Keller, 1994), we conceptualise the German lexicon for the mathematics classroom to be non-static and constantly changing. This is why we choose to present our list of terms as the “current German lexicon”. Starting with the viewing of the stimulus material by a local expert team in Bremen, an initial list of 105 terms describing elements of the mathematics classroom that could be identified by a name was developed. Moreover, this team developed German and English definitions for each of the terms. In a second step, three small groups of experienced teachers were included in a regional evaluation. Each group discussed the list of terms, making suggestions for the addition and deletion of terms. The different regional evaluation groups highlighted further terms they found to be highly relevant. Regional evaluation resulted in a list of 75 terms, which were included in a national online survey. Special emphasis was put on the terms which had been marked as highly relevant in the regional evaluation. The online evaluation process consisted of three steps: Assessing the match between terms and definitions by providing the definitions and asking for the term, assessing the familiarity of teachers with the lexical terms chosen in the local and regional evaluation procedures, as well as assessing the perceived relevance of the terms. An exclusion of terms which were either unfamiliar to teachers, or perceived as scarcely relevant, led to the current German lexicon consisting of 65 main terms and 11 additional synonymous terms. We will further report on ways in which we have integrated the current German lexicon into teacher education in Bremen, ways that both enhance the students’ reflections on their teaching and support the continuing refinement of the German Lexicon. In a practical phase during their studies, students use lexical terms to reflect about their own teaching and the teaching they observed. By observing examples of the lexical items in practice, student and new teachers recognise cases where it played a role in the success of a lesson. We will provide examples from student discussions about different lexical items. Examples and non-examples from their own practice guide student reflection and make the Lexicon a powerful tool for teacher education.

Keller, R. (1994). On language change: The invisible hand in language. London: Psychology Press.