A = no
THEOS = god
An atheist is NOT someone who just doesn't believe in God. It's a person who DOES believe there is NO God. A person who just doesn't believe should be called something else. Maybe "acreist."
The word is not atheos, its atheist. Theist may have derived from the root theos, but the word theist very clearly means believer in a god or gods.
The spelling is different but the meaning is the same. So what I contend remains: If a theist believes in the existence of God, then an atheist believes in the non-existence of God.
You can continue being Mr. Science. I, however, am Mr. Language.