A SocialAgent that is actedBy agents that are (and act as) members of a Collective. A collective agent can have roles that are also roles of those agents. For example, in sociology, a 'group action' is the situation in which a number of people (that result to be members of a collective) in a given area behave in a coordinated way in order to achieve a (often common) goal. The Agent in such a Situation is not single, but a CollectiveAgent (a Group). This can be generalized to the notion of social movement, which assumes a large Community or even the entire Society as agents. The difference between a CollectiveAgent and an Organization is that a Description that introduces a CollectiveAgent is also one that unifies the corresponding Collective. In practice, this difference makes collective agents 'less stable' than organizations, because they have a dedicated, publicly recognizable Description that is conceived to introduce them.