The seven formal divisions within the Aes Sedai, each designated by a colour and following a distinct philosophy. The Blue focuses on causes and justice; the Brown on scholarship and knowledge; the Green (the Battle Ajah) holds itself ready for Tarmon Gai'don; the Grey mediates disputes; the Red hunts men who can channel; the White pursues logic and philosophy; and the Yellow specialises in Healing. A secret Black Ajah, sworn to the Dark One, was long denied but eventually exposed. Before the Trolloc Wars, 'ajah' was an informal term for any temporary association.