Many say the etymology of religion lies with the Latin word religare, which means "to tie, to bind." This seems to be favored on the assumption that it helps explain the power religion has to bind a person to a community, culture, course of action, ideology, etc. The Oxford English Dictionary points out, though, that the etymology of the word is doubtful. Earlier writers like Cicero connected the term with relegere, which means "to read over again" (perhaps to emphasize the ritualistic nature of religions?).

Some argue that religion doesn't even exist in the first place — there is only culture, and religion is simply a significant aspect of human culture. Jonathan Z. Smith writes in Imagining Religion:

"...while there is a staggering amount of data, phenomena, of human experiences and expressions that might be characterized in one culture or another, by one criterion or another, as religion — there is no data for religion. Religion is solely the creation of the scholar's study. It is created for the scholar's analytic purposes by his imaginative acts of comparison and generalization. Religion has no existence apart from the academy."

It is true that many societies do not draw a clear line between their culture and what scholars would call "religion," so Smith certainly has a valid point. This does not necessarily mean that religion doesn't exist, but it is worth keeping in mind that even when we think we have a handle on what religion is, we might be fooling ourselves because we aren't able to distinguish what belongs just to a culture's "religion" and what is part of the wider culture itself.

Functional vs. Substantive Definitions of Religion

Many scholarly and academic attempts to define or describe religion can be classified into one of two types: functional or substantive. Each represents a very distinct perspective on the nature of the function of religion. Although it is possible for a person to accept both types as valid, in reality, most people will tend to focus on one type to the exclusion of the other.

Substantive Definitions of Religion

The type a person focuses on can tell a lot about what he thinks of religion and how he perceives religion in human life. For those who focus upon substantive or essentialist definitions, religion is all about content: if you believe certain types of things you have a religion while if you don’t believe them, you don’t have a religion. Examples include belief in gods, belief in spirits, or belief in something known as “the sacred.”

Accepting a substantive definition of religion means looking at religion as simply a type of philosophy, a system of bizarre beliefs, or perhaps just a primitive understanding of nature and reality. From the substantive or essentialist perspective, religion originated and survived as a speculative enterprise which is all about trying to understand ourselves or our world and has nothing to do with our social or psychological lives.

Functional Definitions of Religion

For those who focus on functionalist definitions, religion is all about what it does: if your belief system plays some particular role either in your social life, in your society, or in your psychological life, then it is a religion; otherwise, it’s something else (like philosophy). Examples of functionalist definitions include describing religion as something which binds together a community or which alleviates a person’s fear of mortality.

Accepting such functionalist descriptions results in a radically different understanding of the origin and nature of religion when compared to substantive definitions. From the functionalist perspective, religion doesn’t exist to explain our world but rather to help us survive in the world, whether by binding us together socially or by supporting us psychologically and emotionally. Rituals, for example, exist to bring us all together as a unit or to preserve our sanity in a chaotic world.

The definition of religion used on this site doesn’t focus on either functionalist or essentialist perspective of religion; instead, it attempts to incorporate both the types of beliefs and the types of functions which religion often has. So why spend so much time explaining and discussing these types of definitions?

Even if we don’t use a specifically functionalist or essentialist definition here, it remains true that such definitions can offer interesting ways to look at religion, causing us to focus on some aspect which we might have otherwise ignored. It is necessary to understand why each is valid to better understand why neither is superior to the other. Finally, because so many books on religion tend to prefer one type of definition over another, understanding what they are can provide a clearer view of authors’ biases and assumptions.

Problematic Definitions of Religion

Definitions of religion tend to suffer from one of two problems: they are either too narrow and exclude many belief systems which most agree are religious, or they are too vague and ambiguous, suggesting that just about anything and everything is a religion. Because it's so easy to fall into one problem in the effort to avoid the other, debates about the nature of religion will probably never cease.

A good example of a narrow definition being too narrow is the common attempt to define "religion" as "belief in God," effectively excluding polytheistic religions and atheistic religions while including theists who have no religious belief system. We see this problem most often among those who assume that the strict monotheistic nature of western religions they are most familiar with must somehow be a necessary characteristic of religion generally. It's rare to see this mistake being made by scholars, at least anymore.

A good example of a vague definition is the tendency to define religion as "worldview" — but how can every worldview qualify as a religion? It would be ridiculous to think that every belief system or ideology is even just religious, never mind a full-fledged religion, but that's the consequence of how some try to use the term.

Some have argued that religion isn't hard to define and the plethora of conflicting definitions is evidence of how easy it really is. The real problem, according to this position, lies in finding a definition that is empirically useful and empirically testable - and it's certainly true that so many of the bad definitions would be quickly abandoned if proponents just put in a bit of work to test them.

The Encyclopedia of Philosophy lists traits of religions rather than declaring religion to be one thing or another, arguing that the more markers present in a belief system, the more "religious like" it is:

Belief in supernatural beings.

A distinction between sacred and profane objects.

Ritual acts focused on sacred objects.

A moral code believed to be sanctioned by the gods.

Characteristically religious feelings (awe, sense of mystery, sense of guilt, adoration), which tend to be aroused in the presence of sacred objects and during the practice of ritual, and which are connected in idea with the gods.

Prayer and other forms of communication with gods.

A world view, or a general picture of the world as a whole and the place of the individual therein. This picture contains some specification of an overall purpose or point of the world and an indication of how the individual fits into it.

A more or less total organization of one's life based on the world view.

A social group bound together by the above.

This definition captures much of what religion is across diverse cultures. It includes sociological, psychological, and historical factors and allows for broader gray areas in the concept of religion. It also recognizes that "religion" exists on a continuum with other types of belief systems, such that some aren't religious at all, some are very close to religions, and some definitely are religions.

This definition is not without flaws, however. The first marker, for example, is about "supernatural beings" and gives "gods" as an example, but thereafter only gods are mentioned. Even the concept of "supernatural beings" is a bit too specific; Mircea Eliade defined religion in reference to a focus on "the sacred," and that is a good replacement for "supernatural beings" because not every religion revolves around the supernatural.

An Improved Definition of Religion

Because the flaws in the above definition are relatively minor, it's an easy matter to make some small adjustments and come up with a much-improved definition of what religion is:

Belief in something sacred (for example, gods or other supernatural beings).

A distinction between sacred and profane spaces and/or objects.

Ritual acts focused on sacred spaces and/or objects.

A moral code believed to have a sacred or supernatural basis.

Characteristically religious feelings (awe, sense of mystery, sense of guilt, adoration), which tend to be aroused in the presence of sacred spaces and/or objects and during the practice of ritual which is focused on sacred spaces, objects, or beings.

Prayer and other forms of communication with the supernatural.

A worldview, ideology, or a general picture of the world as a whole and the place of individuals therein which contains a description of an overall purpose or point of the world and how individuals fit into it.

A more or less complete organization of one's life based on this worldview.

A social group bound together by and around the above.

This is the definition of religion describes religious systems but not non-religious systems. It encompasses the features common in belief systems generally acknowledged as religions without focusing on specific characteristics unique to just a few.