Social studies literature enjoys a wide range of definitions of social movement (Christiansen 2009). This diversity of this definition is due to the fact that theorists tend to define the term social movement according to their particular theoretical formulation (Diani 1992). Therefore, this section will first consider definitions proposed by a group of scholars who represent four main trends in the analysis of social movements. These trends are as follows: the “Collective Behavior Perspective” (Turner and Killian), the “Resource Mobilization Theory” (RMT) (ZaId and McCarthy); the “Political Process Perspective” (Tilly); and the “New Social Movement Approach” (NSM) (Touraine, Melucci). Next, a definition by Della Porta and Diani is selected since this definition has been centered on the most important characteristics of social movements and often cited by researchers. (Turner and Killian 1987) cited in (Diani 1992, p. 4) define social movements as “collectivities that act with some continuity to promote or resist a change in the society or organization of which they are part. As a collectivity, a movement is a group with indefinite and changing members and with a leadership whose position is determined more by the informal response of its members than by formal procedures for legitimizing authority”. Turner and Killian consider a social movement as a peculiar type of collective behavior that opposes regularity and institutional behavior. Furthermore, Turner believes that social movements do not necessarily coincide with movement organizations, although these organizations can carry out many of the movement's tasks and it is often useful to monitor and speak on behalf of movements (Diani 1992). (McCarthy and Zald 1977, p. 1217) def......middle of paper......rain: the need for self-actualization in everyday life” (Melucci 1989, p. 23). What distinguishes contemporary movements from traditional movements is that they are active at various levels within and outside the political sphere. Furthermore (Melucci 1989, p. 75) argues that contomberari movements establish their collective identity outside the political sphere and “translate their action into symbolic challenges that overturn dominant cultural codes”. The differences that have characterized contemporary social movements – the construction of unity in the face of heterogeneity and differentiation, the creation of symbolic challenges and their political characters – make it difficult to be approached by the theories mentioned above which are politically reductionist and limit themselves to analyze the outcomes of actions or movements (Barholomew & Mayer 1992).