Atheism, in its broadest sense, is an absence of belief in the existence of gods. This definition includes as atheists both those who assert that there are no gods, and those who make no claim about whether gods exist or not. Narrower definitions, however, often only qualify those who assert there are no gods as atheists, labeling the others as agnostics or simply non-theists.
The Greek word "atheoi"αθεοι ("without God, knowing and worshipping no God") as it appears in the Epistle to the Ephesians 2:12, on the early 3rd-century Papyrus 46.
Although atheists often share common concerns regarding empirical evidence and the scientific method of investigation and a large number are skeptics, there is no single ideology that all atheists share. Additionally, there are certain individuals whose religious or spiritual beliefs some might describe as atheistic, though those holding such beliefs do not normally describe themselves as atheists.
Atheism includes, but is not equivalent to, the position of antitheism, the active opposition to theism.
In early Ancient Greek, the adjective atheos (from privative a- + theos "god") meant "without gods" or "lack of belief in gods". The word acquired an additional meaning in the 5th century BCE, expressing a total lack of relations with the gods; that is, "denying the gods, godless, ungodly", with more active connotations than asebēs, "impious". Modern translations of classical texts sometimes translate atheos as "atheistic". As an abstract noun, there was also atheotēs: "atheism". Cicero transliterated atheos into Latin. The discussion of atheoi was pronounced in the debate between early Christians and pagans, who each attributed atheism to the other.