Learning Assistants (LAs) are undergraduate peer-tutors who, having successfully passed a particular course, return to assist with teaching that course. Through their work across many STEM courses, LAs have been shown to have positive effects on several student outcomes, but little is known about why LAs' presence in classrooms is positively associated with these outcomes. This study provides a novel perspective on this issue by critically analyzing a portion of classroom dialog between an LA and a student in a Calculus I course. The language used by these interlocutors was analyzed with attention to the social and informational aspects of the dialog, examining both the relationship between the student and the LA, and the ways they frame mathematical content. These findings have implications for the future study of LAs' practice and bear relevance to the improvement of LA educational programs. [For the complete proceedings, see ED658295.]