Is atheism/non-adherence a religion?
No. Atheism is only a concept and does not include any sort of rituals, laws, prayers or requirements of those who would consider themselves atheist. The position affirms the nonexistence of gods or rejects theism, and nothing more. As such, those with some other sort of faith or belief system that does not include that of a deity could consider themselves atheist. For example, a Buddhist could consider themselves atheist without any conflict to their beliefs. Although people who call themselves atheists do tend to be anti-religious, some are still spiritual or religious in one way or another. Atheism does not preclude systems of belief, just the idea of a deity.