Hey @Imre — I approved your tag wiki edits for wide-angle and ultra-wide-angle since there was nothing at all there before, but, citation needed on your sensor-size-related definitions. Sounds plausible but I'd like to see a reference, and maybe an update to:
I think I heard this first at an open university photography course some years ago (a real one, not the imaginary one that gives me hard assignments). I don't even remember the name of my mentor there, so I can't pass this as a reference. Wikipedia seems to agree, but cannot be used as a credible reference by itself and is missing citation also.
I added link to our relevant question into those tag wiki bodies, and will add my answer there when I find some better references.