The meaning of words is determined by how people actually use them.
Exactly!
Some words are stretched a bit thin trying to cover a range of meanings. If you really want to know what someone believes, feels, "knows" about god then ask them don't expect a single word to get it right.
Each of 'theist', 'agnostic' and 'atheist' covers some range of meanings with just a bit of possible overlap on the extremes of each. All that you can tell from such labels is a 'theist' is going to be one who gives some degree of credance to the existance of some kind of god like entity, and 'atheist' is not going to give any and the agnostic will overlap on the extremes with each.
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