This report details an exploratory study that employs qualitative methods to characterize the academic language used by teachers and students in 4 th and 5 th grade mainstream science classrooms. Teacher oral language, and to some degree student talk, was observed during content instruction. This type of data allows for a broad descriptive representation of language use and vocabulary choice rather than fine- grained structural analyses. Print materials and student written products were also examined in this manner. Primary research questions include (1) how does teacher language function in the classroom? (2) how do teachers support academic vocabulary growth? The inductive approach taken led to the development of a matrix of teacher- produced academic language within three instructional contexts; concept instruction, vocabulary instruction, and process/application instruction. Describing the language embedded in oral and written classroom discourse has implications for both educational research and practice. The focus on mainstream classroom talk will serve as a baseline for future research of academic language and English language learners. Specifically, this study has created a conceptual framework with empirical illustrations that should prove valuable for (1) conducting further study of effective classroom instruction that includes academic language, and (2) the development of language assessments that measure student progress towards academic language proficiency.