The word religion is sometimes used interchangeably with faith or belief system; however, in the words of Émile Durkheim, religion differs from private belief in that it is "something eminently social".

A global 2012 poll reports that 59% of the world's population is religious, 23% are not religious, and 13% are atheists.

There are numerous definitions of religion and only a few are stated here. The typical dictionary definition of religion refers to a "belief in, or the worship of, a god or gods" or the "service and worship of God or the supernatural".

However, writers and scholars have expanded upon the "belief in god" definitions as insufficient to capture the diversity of religious thought and experience.

Edward Burnett Tylor defined religion as "the belief in spiritual beings".

He argued, back in 1871, that narrowing the definition to mean the belief in a supreme deity or judgment after death or idolatry and so on, would exclude many peoples from the category of religious, and thus "has the fault of identifying religion rather with particular developments than with the deeper motive which underlies them". He also argued that the belief in spiritual beings exists in all known societies.

The anthropologist Clifford Geertz defined religion as a "system of symbols which acts to establish powerful, pervasive, and long-lasting moods and motivations in men by formulating conceptions of a general order of existence and clothing these conceptions with such an aura of factuality that the moods and motivations seem uniquely realistic.

Alluding perhaps to Tylor's "deeper motive", Geertz remarked that "we have very little idea of how, in empirical terms, this particular miracle is accomplished. We just know that it is done, annually, weekly, daily, for some people almost hourly; and we have an enormous ethnographic literature to demonstrate it".

The theologian Antoine Vergote also emphasized the "cultural reality" of religion, which he defined as "the entirety of the linguistic expressions, emotions and, actions and signs that refer to a supernatural being or supernatural beings"; he took the term "supernatural" simply to mean whatever transcends the powers of nature or human agency.