The "Scarlet A" of the Out Campaign
Atheism (from the Greek a-, meaning "without", and theos, meaning "god") is the absence of belief in the existence of gods.
Theos includes the Abrahamic YHWH(s), Zeus, the Flying Spaghetti Monster, and every other deity from A to Z (and 0-9, !, ", #, $ or any other character, obviously). For the definition of atheism, the terms "God" and "a god" are used interchangeably as there is no difference between a monotheistic deity and a polytheistic pantheon of deities when it comes to complete disbelief in them. This also has the deliberate intent of ignoring the privileged position Yahweh has held in English grammar. Most atheists also do not believe in anything supernatural or paranormal (someone like this would be considered a naturalist, or even a materialist).