Classroom talk is regarded as essential in engaging and developing student understandings in the domain of mathematics. The process of classroom talk, however, may occur in quite different ways. In this paper we analyse two forms of classroom talk - replacement and interweaving. These provide a heuristic for considering how teachers might develop a repertoire of practices that they may deploy to afford student learning. In an analysis of student talk in a Year 7 classroom we found that replacement and interweaving can facilitate learning. We conclude that teachers should use classroom talk formats reflectively and intentionally in their classrooms to afford students a range of opportunities to develop their mathematical thinking.