Religion is a wide-ranging set of ideas and practices about the world, life, death, morality, truth, Scripture, deity, God, belief, prayer, ritual, conformity, culture, society, tolerance, morality, family, and more. It has a complex and sometimes troubled impact on the lives of individuals and groups globally. It is so broad a concept that it is difficult to find a way to define it without including beliefs or practices that most people do not regard as religious.
A traditional approach defines religion as a set of beliefs and practices that promote the existence of an unusual kind of reality. The idea behind this is that, once the phenomenon has been defined in terms of such beliefs and practices, it will have distinctive characteristics. Those characteristics can then be used to distinguish it from other phenomena. This approach is called a “substantive” definition.
An alternative approach is to define religion as a functional category. In this view, a social kind emerges when certain sets of activities unite a group or society into a moral community. It is a different idea from the substantive definition, but it can have the same sort of power to discriminate among phenomena and to develop explanatory theories about them. This is the approach of Emile Durkheim.
Both approaches are prone to problems. Substantive definitions might be too inclusive, for example including people who believe in fate or magic. Polythetic definitions might also have difficulty in identifying enough characteristics that would satisfy the threshold requirement.