an ideology grounded in the belief that without doubt there exist no deities, by any definition that might be given to the term. Often characterised by a further belief that all people should, or will in the future, hold to the same ideology.
an ideology grounded in the belief that specific gods claimed by Abrahamic religions do not exist.
the position that there is no empirical evidence for any deities, and so claims that some god or other necessarily exists can be reasonably challenged. Often supplemented by the more tenuous stance that until there is evidence it is reasonable to assume that there exist no gods.
the position that gods do not exist independently of human invention.
the position that gods do not exist independently of human invention, what is constructed by humans is not, in some important sense, real, ergo there are definitively no deities existent.
a set of positions inclusive of some or all of the following: 1) that claims that gods exist for a certainty are in error, 2) that gods are not necessary, and 3) that there may well be nothing existent that corresponds to the term by any definition given to it.
(n.b. these atheisms are clearly not all mutually exclusive)