Atheism is the doctrine or belief that there is no god. In contrast, the word agnostic refers to a person who neither believes nor disbelieves in a god or religious doctrine. Agnostics assert that it’s impossible to know how the universe was created and whether or not divine beings exist.

Non-religious people may be atheists, which means that they don't see any reason to believe there is a god. They can also be agnostic, meaning they accept that we can't know for certain whether or not a god exists. Many people are both agnostic and atheist at the same time.

The meaning of NONBELIEF is absence or lack of belief; especially : absence or lack of religious belief.