[haunter]

That made me wonder, UNIX is also trademarked https://unix.org/trademark.html

And there are handful of OSes registered as UNIX Certified https://www.opengroup.org/openbrand/register/

Yet there is no single "UNIX OS"

[Oxidation]

The AT&T Unix is probably "the" Unix, if there is one, but the name got sold eventually to The Open Group which licenses it to compliant systems.

So it's now a bit more like x86 (family of similar products that work somewhat similarly, though x86 doesn't need a license any more) rather than Pentium (a product or range from a specific company).