The most common question asked here is WHO or WHAT is an atheist.
Atheist: a person who disbelieves or lacks belief in the existence of God or gods.
The dictionary definition of “atheist” is (Merriam-Webster): a person who does not believe in the existence of a god or any gods. Thus, an atheist is someone who lacks belief in a god or gods. To be more precise: atheism in its basic form is not the active belief that there is no god (singular or plural), but the absence of active belief in a god/gods. No more, no less.
Agnostic atheism: lack of belief in any god, combined with the realisation that the existence or non-existence of any god is not knowable, and can not be proven or disproven.
Strong atheism: in addition to a lack of belief in any god, the strong atheist makes the positive claim that no god(s) exist.