Linguistic Fundamentals of Teaching: A Content-Based Approach for English Language Learning is an accessible introduction to linguistics, designed specifically for teachers working with English language learners across content areas. Rather than treating linguistics as a separate discipline, this text positions it as the backbone of effective language instruction, offering a clear foundation for understanding the challenges and communicative needs of multilingual students. Chapters explore key topics including first and second language acquisition, morphology, semantics, phonology, orthography, reading, syntax, and pragmatics. Each chapter integrates practical activities drawn from real classroom contexts across the humanities, arts, mathematics, and the physical and social sciences. As they work through the text, teachers engage with LiFT (Linguistic Fundamentals of Teaching) activity plans that combine linguistic theory with subject-area instruction. These plans support pronunciation, vocabulary development, meaning-making, sentence formation, and social language use, all rooted in the authentic content of their own teaching. What sets this book apart is its commitment to making linguistics actionable. It offers not just theory but concrete strategies teachers can apply immediately to support English learners in content-rich classrooms. Designed for both pre-service and in-service teachers, including those in applied linguistics and TESOL programs, it offers not just theory but a practical toolkit of strategies that can be applied immediately in content-area classrooms to support English learners effectively.