As a behavior analyst working with clients to effect change, words matter. Understanding complex language allows you to skillfully navigate your work to help clients build better lives. Relational frame theory (RFT) suggests the main building block of Language and cognition is relating-the ability to flexibly respond to links between one thing and another, generating new connections in the process (that is, derived relational responding and transformations of function). This professional guide outlines the principles of RFT, and offers practical applications and tools to enhance your practice. With a focus on establishing psychological flexibility, prosociality, and cooperative contexts for change at all levels of analysis, Understanding and Applying Relational Frame Theory provides a comprehensive overview of RFT to help you use language effectively in your work and life. You'll learn to apply a behavior analytic understanding of complex language to a variety of settings-including education, mental health, and business. You'll discover how complex verbal repertoires affect individual behavior, as well as how relational framing functions in the context of groups. Finally, you'll learn how RFT can be applied to issues of diversity, equity, and inclusion-as well as global sustainability.