Uit ArchiMate:"A business process or function may be interpreted as the internal behavior assigned to a single business role. In some cases behavior is the collective effort of more than one business role; in fact a collaboration of two or more business roles results in collective behavior which may be more than simply the sum of the behavior of the separate roles. Business collaborations represent this collective effort. Business interactions are used to describe the internal behavior that takes place within business collaboration. A collaboration is a (possibly temporary) collection of roles within an organization which perform collaborative behavior (interactions). Unlike a department, which may also group roles, a business collaboration does not have an official (permanent) status within the organization; it is specifically aimed at a specific interaction or set of interactions between roles. However, a business collaboration can be regarded as a kind of 'virtual role', hence its designation as a specialization of role. It is especially useful in modeling B2B interactions between different organizations.
A business collaboration may be composed of a number of business roles, and may be assigned to one or more business interactions. A business interface or an application interface may be used by a business collaboration, while a business collaboration may have business interfaces (through composition). The name of a business collaboration should preferably be a noun. It is also rather common to leave a business collaboration unnamed."