Definitions of religion are not used only by scholars but also by a wider public, politics, law and various religious communities. In contrast to the scientific definitions, which are as a rule open, including a majority of the active new religious movements, popular definitions are considerably narrower,allowing only slight deviations from the dominating Christian forms of religion. Institutional definitions usually aim at the middle way between the expert and the popular definitions. Despite the apparent inability to forma universally valid definition, social scientists should not withdraw the ambition to define religion. However, a pragmatic approach, which derives fromthe usefulness of a particular definition in a certain context, should be taken into account.