Language itself is a common set of symbols and pointers providing for a shared set of mental models amongst various actors. Generally the most common definition should be the guiding one, much as the most preferred medium of payment becomes a de facto currency (and for many of the same reasons).

If you want a standard definition of capital I'd suggest looking at those provided by a source such as Investopedia or leading economics texts, probably Paul Krugman or Gregory Mankiw's, though there are many, with one fair list at Reddit's /r/Economics: https://www.reddit.com/r/Economics/wiki/reading. Otherwise, you might hit up DDG for econ 1 or econ 101 syllabi and recommended readings.

If you're looking for the broadest possible set of definitions, well, there are many, with varying levels of acceptance, but the answers probably aren't particularly useful.

Another possible angle would be to ask what I personally think about factors of production, and what they are. My thoughts are in flux. And, as a Space Alien Cat, they frequently have little or no real world significance or impact.

Steve Keen, though, is doing some very interesting work, in and since Debunking Economics, and I'd strongly urge following him. Among other elements, he's looking at the role of energy in economic production (he's one of numerous people to have done so, over the past century or more, though the idea's never really caught on, far the worse reflection on the economic orthodoxy than the notion itself).

I've been looking at the question of what technology itself is, or more specifically, what its mechanisms, of which I've identified roughly nine: fuel and fuel-based systems, energy transmission and transformation, materials, technical knowledge, scientific knowledge, information, networks, systems, and hygiene factors. (Concept still under development, some discussion at https://dredmorbius.reddit.com) It's recently occurred to me that virtually all of these are factors of production, though they're not all the factors of production.

There's the question of what labour itself is, and what its components and mechanisms are, and how they've changed. It's useful to keep in mind that until roughly 1800, a tremendous percentage of actual motive force was supplied by human or animal muscle. And our sense of what these contribute has changed markedly. The present formulation of labour does have many elements of capital to it, and that's reflected in extant terminology (e.g., "human capital" and "intellectual capital"), so your observations have some validity and currency.

As noted above, much of the mainstream factors-of-production has far more to do with tracking payments than functional mechanisms. I see considerable room for refinement.