Academic language pervades educational standards and teacher evaluation systems for teacher licensure and is a skill that all educators across grades must teach. Despite its common use, this term may be less understood in schools. This article explores a mixed-method study to examine differences in K-12 teachers' knowledge of the linguistic characteristics of academic language, motivations for incorporating academic language instruction, and their interpretations of this term. Survey data and open-ended responses were collected from 322 teachers, multiple regression was employed to explore teachers' academic language knowledge and motivation, and content analysis was used to examine teacher interpretations of this term. Results indicate that teachers with language development-focused endorsements had higher motivation than those without and that teachers with less knowledge conceptualized academic language as unidimensional or in ways that privileged certain students.