The way I see it:

(1) There is kind of a definition of a chair. But it's very long. Like, extremely long, and includes maybe even millions to billions of logical expressions, assuming your definition might need to use visual or geometric features of a given object to be classified as a chair (or not chair).

This is a kind of unification of neural networks (in particular LLMs) and symbolic thought: large enough symbolic thought can simulate NNs and vice versa. Indeed even the fact that NNs are soft and fuzzy does not matter theoretically, it's easy to show logical circuits can simulate soft and fuzzy boundaries (in fact, that's how NNs are implemented in real hardware! as binary logic circuits). But I think specific problems have varying degrees of more natural formulation as arithmetic, probabilistic, linear or fuzzy logic, on one hand, and binary, boolean-like logic on the other. Or natural formulations could involve arbitrary mixes of them.

(2) As humans, the actual definitions (although they may be said to exist in a certain way at a given time[1]) vary with time. We can, and do, invent new stuff all the time, and often extend or reuse old concepts. For example, I believe the word 'plug' in english likely well predates modern age, probably used to refer to original electrical power connectors. Nowadays there are USB plugs, which may not carry power at all, or audio plugs, etc. (maybe there are better examples). In any case the pioneer(s) usually did not envision all a name could be used for, and uses evolve.

(3) Words are used as tools to allow communication and, crucially, thought. There comes a need to put a fence (or maybe a mark) in abstract conceptual and logic space, and we associate that with a word. Really a word could be "anything we want to communicate", represent anything. In particular changes to the states of our minds, and states themselves. That's usually too general, most words are probably nouns which represent classifications of objects that exist in the world (like the mentioned chair) -- the 'mind state' definition is probably general enough to cover words like 'sadness', 'amazement', etc., and 'mind state transitions' probably can account for everything else.

We use words (and associated concepts) to dramatically reduce the complexity of the world to enable or improve planning. We can then simplify our tasks into a vastly simpler logical plan: even something simple like put shoes, open door, go outside, take train, get to work -- without segmenting the world into things and concepts (it's hard to even imagine thought without using concepts at all -- it probably happens instinctively), the number of possibilities involved in planning and acting would be overwhelming.

Obligatory article about this: https://slatestarcodex.com/2014/11/21/the-categories-were-ma...

---

Now this puts into perspective the work of formalizing things, in particular concepts. If you're formalizing concepts to create a system like Cyc, and expect it to be cheap, simple, reliable, and function well into the future, by our observations that should fail. However, formalization is still possible, even if expensive, complex, and possibly ever changing.

There are still reasons you may want to formalize things, in particular to acquire a deeper understanding of those things, or when you're okay in creating definitions set in stone because they will be confined to a group being attentive and restrictive to their formal definitions (and not, as natural language, evolving organically according to convenience): that's the case with mathematics. The peano axioms still define the same natural numbers; and although names may be reused, you can usually specify them to a particular axiomatic definition that will never change. And thus we can keep building facts on those foundations forever -- while what is a 'plug' in natural language might change (and associated facts about plugs become invalid), we can define mathematical objects (like 'natural numbers') with unchanging properties, and ever-valid and potentially ever-growing valid facts to be known about them, reliably. So fixing concepts in stone more or less (at least when it comes to a particular axiomatization) is not such a foolish endeavor it may look like, quite the opposite! Science in general benefits from those solid foundations.

I think eventually even some concepts related to human emotions and specially ethics will be (with varying degrees of rigor) formalized to be better understood. Which doesn't mean human language should (or will) stop evolving and being fuzzy, it can do so independently of formal more rigid counterparts. Both aspects are useful.

[1] In the sense that, at a given time, you could (theoretically) spend an enormous effort to arrive at a giant rule system that would probably satisfy most people, and most objects referred to as chairs, at a given fixed time.