In the context of archaeology.... a good starting point would be
https://www.researchgate.net/publication/344644569_Definitio...
Yes, the dividing lines are blurry.
No, it is not totally subjective
That's a lot of different kinds of definitions, some overlap, other disagree. Seems to me a similar problem with naming and categorizing -- whether it is something useful (as a framework for thinking through things), or for communication. They all create biases in how we see things, and it isn't as if it is something intrinsic to the known universe says, that is a city.