Circularity and linearity are two essential terms in the theory and practice of couples and family therapy. Understanding the distinctions between circularity and linearity as well as their clinical applications opens the door to exploring important historical shifts that helped birth and later improve the couples and family therapy field. This entry first defines circularity and linearity, discusses the implications of circularity, and gives examples of circularity. It then discusses feminist critiques of circularity and describes the both/and approach that incorporates circularity and linearity. Finally, it explores how circularity and linearity apply to couples and family therapy.