With a focus on what mathematics and science educators need to know about academic language used in the STEM disciplines, this book critically synthesizes the current knowledge base on language challenges inherent to learning mathematics and science, with particular attention to the unique issues for English learners. These key questions are addressed: When and how do students develop mastery of the language registers unique to mathematics and to the sciences? How do teachers use assessment as evidence of student learning for both accountability and instructional purposes? Orienting each chapter with a research review and drawing out important Focus Points, chapter authors examine the obstacles to and latest ideas for improving STEM literacy, and discuss implications for future research and practice.