A corporate group or group of companies is a collection of parent and subsidiary corporations that function as a single economic entity through a common source of control. The concept of a group is frequently used in tax law, accounting and (less frequently) company law to attribute the rights and duties of one member of the group to another or the whole. If the corporations are engaged in entirely different businesses, the group is called a conglomerate. The forming of corporate groups usually involves consolidation via mergers and acquisitions, although the group concept focuses on the instances in which the merged and acquired corporate entities remain in existence rather than the instances in which they are dissolved by the parent. The group may be owned by a holding company which may have no actual operations.