The purpose of this study was to identify the interactional strategies that one teacher used in a discourse-rich tenth-grade classroom to develop her students' facility with the mathematical register. Viewing the mathematical register as multi-semiotic and having a specific grammatical patterning, we used discourse analysis (Sinclair & Coulthard, 1975) to examine the teacher's initiation and feedback moves that supported students in using symbolic and natural language in mathematical ways during three consecutive lesson episodes. Our findings suggest that, while teacher interactional strategies which focus or probe student thinking are effective for supporting students' learning of the mathematical register, strategies that funnel or lead student contributions towards predetermined answers may also serve that purpose through creating opportunities for meaningful language practice.