This chapter deals with more aggregated social forms, with two generic notions on the side of entities: networks and collectives. Since the relations that form the basis of networks are considered to be dyadic collectives (involving two entities), the two terms need to be defined in a single move. Since collectives are defined in terms of the sharing of resources by individuals, this chapter also addresses the process side by defining the notion of sphere of activity as a set of activities sharing resources. The notion of institution completes these definitions, denoting the assemblies of coordinating resources that hold collectives or explicit spheres of activity together.