This study examined discussions centered on precise mathematical language use in two fifth grade classrooms. Drawing on episodes from lessons in which teachers focused on encouraging mathematics reasoning, our analysis examines the relationship between precise language use and mathematical justifying. We present three classroom episodes that illustrate facets of the relationship between precise language use and mathematical argument, and explore how blurring the borders of two types of pedagogical tools (attention to precise mathematical language and engagement of students in justifying) promotes enculturation of students into mathematics. [For the complete proceedings, see ED583608.]