The Reading League defines the science of reading as "a vast, interdisciplinary body of scientifically-based research about reading and issues related to reading and writing." Researchers from fields of cognitive science, psychology, neurobiology, education, and implementation science are contributing to our developing understanding and knowledge of the brain processes necessary for reading, the reasons for reading struggle, and how to teach reading best. The science of reading is important because it helps teachers use practices that are more likely to be effective. For too long teachers taught in ways that may have worked for some readers but failed for too many. The science of reading shows us what to teach, how to teach it, and why it works. The term structured literacy is often used synonymously with science of reading. Structured literacy focuses instruction on the explicit use of letter-sound knowledge to read. Key tenants are: instruction that is systematic, cumulative and sequential, providing opportunities for practice, having high levels of interaction between the teacher and students, giving corrective feedback, instruction that is data-informed, and tailoring instruction to the needs of the learner.