The scale I have seen used includes the terms “mild, moderate, severe, profound”…
… ah. Here’s a chart that might help:
https://www.asha.org/public/hearing/degree-of-hearing-loss/
I’m not an audiologist so while this is a great question I don’t have these answers at my fingertips :)
At any rate, my “definition” was intended to clarify what mainstream meant in this context.
I have seen folks make a related distinction: born deaf or lost hearing.
Then there are some categories which are defined by physiology: some folks can't receive any benefit from cochlear implants because the biological hardware isn't there to interface with.
This just blows my mind: There are folks who fall into the subset of a subset of a subset and thus are so different from me that it's hard to imagine what it is like to be them, and yet, through ASL for example, or games, or so many things, it becomes apparent that they are just like me--and again, not at all. Minds are neat.