Within social movement theory, collective identity refers to the shared definition of a group that derives from its members’ common interests, experiences, and solidarities. It is the social movement's answer to who we are, locating the movement within a field of political actors. Collective identity is neither fixed nor innate, but rather emerges through struggle as different political actors, including the movement, interact and react to each other. The salience of any given collective identity affects the mobilization, trajectory, and even impacts of social movements. Consequently, collective identity has become a central concept in the study of social movements.