Integration may be defined as a mutual relationship between the whole and its units. If social system is taken to be the whole, unity is necessary for the integration of all the sub-systems within it. Likewise, group is considered to be the unity of its units.
According to Ogburn and Nimkoff, the process of creating a single unit by joining different parts is integration. The process of integration creates a new whole by joining different parts; therefore, integration is also the process of organisation.
Integration in the group means mutual ties among its members. The quality of ties may differ from group to group. Integration has two aspects – one is the process of integration and the other is the unified conditions. As a process, integration always goes on in society. Social system keeps changing and the units keep adjusting themselves accordingly. Sometimes change in the single unit also changes the whole system. Integration is the balance between the whole and its units. When this balance is disrupted disintegration begins in the system.