This edited volume provides a comprehensive overview of theory and research on friendship, which represents one of our most fundamental and unique forms of close relationships. The book comprises sixteen chapters that focus on both the beneficial and detrimental aspects of this important bond. The topics covered include the ways in which friendship varies across the life span, how friendship interacts with gender, and friendship in different contexts, such as in the workplace and through social media, and with different partners, such as mentors, romantic partners, and pets. How friendships are successfully maintained and friendships role in mental, physical, and social functioning is also considered. The contributors come from a variety of scientific disciplines and countries. The book may be used in undergraduate or graduate courses in various fields, including psychology, sociology, counseling, social work, communication, family studies, marriage and family therapy, and nursing.