What do you call a person who doesn't believe in god?

 Atheist don't believe in God. Agnostic don't bother about God although they might recognise the existence.

It is also very subjective as to whether the person's God refer to, nature, truth,and love, which not common in mainstream religion that conventionally set of rules, regulation and ritual. Such religion are like Shintoism and animalism is more spiritual and primitive.