Talking with others about ideas and work is fundamental to learning. But not all talk sustains learning. For classroom talk to promote learning it must be accountable to the learning community, to accurate and appropriate knowledge, and to rigorous thinking. Accountable Talk practices seriously respond to and further develop what others in the group have said. It puts forth and demands knowledge that is accurate and relevant to the issue under discussion. Accountable Talk practices use evidence appropriate to the discipline (e.g., proofs in mathematics, data from investigations in science, textual details in literature, documentary sources in history) and follow established norms of good reasoning.