Augustus
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Religion appears to be....a fairly recent* and Western concept.
*17th century.
And very much in a Christian context.
All definitions of religion will therefore be based on how much a belief system resembles Christianity.
Hence people will use terms like worship, god, supernatural, belief, etc. in their definitions which exclude many other religions.
Not similar enough to Christianity, not a religion.
There is no meaningful way to differentiate religions from non-religious belief systems that is not culturally or historically biased (towards Christianity as a normative religion).
Religion is a useful shorthand in conversation, but as a meaningful category it's somewhat useless and confuses more than it enlightens.