Many of the students who enter my community college world religions courses each semester (and much, for that matter, of the general American public, of whom such students probably represent a fairly representative sampling), sometimes seem to exhibit varying degrees of confusion over the exact meaning of terms such as atheism and agnosticism.

Some simply are unclear on the precise difference between the two. A few seem to harbor profound misunderstandings of the terms (such as when atheists are occasionally confused with, or are accused of being, Satanists or devil worshippers, for instance).

Some clarification of these frequently confused or misconstrued terms may be helpful, therefore.

To begin with, the term “theism” literally means “god-ism” (from the Greek theos, “god”), and by itself simply refers to a belief in the reality of a deity (or deities).

That basic but rather broad and general term can be made much more precise by simply modifying it with a few well-chosen prefixes.

For instance, the prefix mono- derives from the Greek for “one,” “sole,” “singular,” or “alone” (as used in words like monochrome, monogamy, monophonic, monopoly, monotonous, etc.). If we add mono- (“one”) to theism (“god-ism”), then we end up with monotheism (literally “one-god-ism”).

Monotheism therefore refers specifically to a belief in the reality or existence of just one single God alone, to the exclusion of any and all other gods. Judaism, Christianity, and Islam, each of which affirms the existence of one (and only one) God, are classified as monotheistic religions.

Likewise, the prefix poly- derives from the Greek for “many” or “multiple” (as in polygamy, polygon, polymath, polyunsaturated, etc.). If we add poly- (“many”) to theism (“god-ism”), then we end up with polytheism (literally “many-gods-ism”).

Polytheism therefore refers specifically to a belief in the reality or existence of many or multiple gods, rather than just one. Many bygone religions of antiquity, such as those of ancient Greece, Rome, Egypt, and Babylon, worshipped entire pantheons of gods and goddesses.

The prefix a- basically means “non-” or “not-,” and so negates the very term to which it is applied, in effect turning that original term into its polar opposite. Think, for example, of moral/amoral, or historical/ahistorical, or symmetrical/asymmetrical, or sexual/asexual.

So, when a- (“not” or “non”) is added to theism (“god-ism”), then the result is atheism (literally “non-god-ism,” or “no-god-ism”).

Atheism can actually mean a couple of things. It can refer to a belief in the unreality or non-existence of any God or gods; alternately, it can also refer to a mere lack of belief in any God or gods.

What’s the difference? Well, it’s subtle; but it’s also critical.

(To be continued, in Part Two.)