It is tremendously difficult, perhaps impossible.

A chair is something you can sit on (but you can also sit on a rock)

&& it has a backrest (but the foot of a tree serves as a backrest)

&& it elevates you off the floor (but not all chairs take you above floor level very much)

&& it is manmade.

Eg, a chair is any object whose primary purpose is to sit a single individual

If it's meant to seat multiple people, it's a bench, a sofa, etc, but not a chair

If it's meant to be extra comfortable, it might be a single-seat sofa, but this itself a chair

If it's a rock, but positioned such that it's primary purpose is to sit an individual, such as next to a table, then it's a chair.

And most notably, primary purpose is subjective -- it might be understood as a chair, or as a doorstop, depending on your viewpoint, and what you use it for.

To sit an individual at close to, or at, a right angle in regards to their legs

A small rock versus a big rock; Approximating a squat, or standing, is out of bounds

But a stool may consistute a chair when sitting a child

Regardless, I'm mainly talking about the approach to defining it, and that definition by purpose rather than structure is more likely to find a correct definition, not that my example definition is sufficient

So is a zabuton[1] a chair?

[1] https://www.dharmacrafts.com/01_zb/zabuton-mat

It's a game you cannot win.

There are also ergo chairs that you "kneel" on instead!

EDIT: Addendum: It may also be worth asking what definition of truth you're using if we're going to be getting into philosophical arguments about what things are: https://en.wikipedia.org/wiki/Truth

1. A fish, and a flatworm.

2. The end parts of an anchor.

3. The fins on a whale's tail.

4. A stroke of luck.

The meanings are etymologically distinct (for the most part) and it's only chance they ended up wit the same spelling and pronunciation.

If that's philosophically troublesome, linguistics is not for you.

That is, when we refer to a word like “chair” we use quotes, but without the quotes, we can say that an accounting department chair is not a chair.

Alternatively, we could analyze “accounting department chair” as a use of metonymy.

  Virions
  Viroids
  Satellites
  Prions
  Defective interfering particles (DIPs)

[0] https://en.wikipedia.org/wiki/Virus_classification#Subviral_...

[1] https://en.wikipedia.org/wiki/Transfer_RNA

> in the scientific communities

"Is it alive? <long property checklist> Yes/No" is an example of K-12 science education content diverging from science community practice. Both by emphasizing a little used concept, and by being inconsistent with community use.

With bonus points for it being... widely taught; taught as if it were science; an unnecessary hook for learning a set of properties; and an incoherently unfruitful predicate.

I don't know if there's a real name for such? I call them science-education-isms.

Google trends has data to 2004. "living nonliving"[1], aside from being a school-year detector, seems to show a 3x increase in the 2010's?

I'll also link [2], but I don't know what to make of it.

[1] https://trends.google.com/trends/explore?date=all&q=living%2... [2] https://books.google.com/ngrams/graph?content=living+and+non...