In 1965 the American psychologist Bruce Tuckman published “Developmental sequence in small groups” in the Psychological Bulletin. He was then at the Naval Medical Research Institute. The paper named four stages in the life of a group: forming, storming, norming and performing.
In 1977 Tuckman and Mary Ann Jensen added a fifth stage, adjourning. A summary on infed.org, drawing on Donelson Forsyth’s textbook, describes it this way: “Adjourning involves dissolution. It entails the termination of roles, the completion of tasks and reduction of dependency.”