The word religion is commonly used in ordinary language today to refer to a group of people who engage in a set of social practices. This is actually the most critical change in the history of the concept of religion, which first happened when the word was used as a social genus that included Christian and non-Christian groups as species. A good example of this was Edward Herbert’s (1583–1648) writings (Five elements of a religion per Herbert).
Religion as a social genus was used by European Christians in categorizing the cultures they encountered in their colonial ventures. As an example, see the work of Edward Burnett Tylor (1832–1917) (Religion is a belief in spiritual beings per Tylor).
The concept of religion as a social genus evolved to encompass, in order, theistic, polytheistic, then cosmic criterion. The cosmic criterion articulated by William James (religion involves a belief in an unseen order per James) is now the most dominant.
References
Schilbrack, K. (2022). The Concept of Religion. In E. N. Zalta (Ed.), The Stanford Encyclopedia of Philosophy (Summer 2022). Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/archives/sum2022/entries/concept-religion/
It is common today to take the concept religion as a taxon for sets of social practices
the concept is today used for a genus of social formations that includes several members, a type of which there are many tokens.
The most significant shift in the history of the concept is when people began to use religion as a genus of which Christian and non-Christian groups were species. One sees a clear example of this use in the writings of Edward Herbert (1583–1648).
The concept religion understood as a social genus was increasingly put to use by to European Christians as they sought to categorize the variety of cultures they encountered.
The most influential example is that of anthropologist Edward Burnett Tylor (1832–1917)
one can think of the growth of the social genus version of the concept religion as analogous to three concentric circles—from a theistic to a polytheistic and then to a cosmic (or “cosmographic” [Dubuisson 1998]) criterion. Given the near-automatic way that Buddhism is taken as a religion today, the cosmic version now seems to be the dominant one.