does sleep "exist"?

[Standandwait]

I have a 15yo with ASD, and today was trying to explain for him the difference between living and existing. So I came up with a distinction between things that don't exist (ghosts), things that exist (cars, trees, people), things that are alive (trees, people), and living things that are sentient (people, animals).

He promptly asked me, does sleep exist? What do you all think? It's real, sleep, but is it something that "exists" or is it just an idea or a state of being, sort of a verb-turned-into-a-noun?

This probably needs "Philosophers' Corner" rather than "Pedants' Corner"! Sleep is a state that surely has an existence, because we can point to people or animals in that state (and objectively measure the difference it makes to bodily function).

Does happiness exist? Does the number "2" exist? Does morality exist?

I'd say no, sleep does not 'exist', it has no form or physical substance.

A number of verbs are also nouns depending on context (eg. Running, or to be on 'a run'), I don't think that's necessarily special about the verb to sleep.

I'd say that 'sleep' like 'happiness' is an abstract noun, and that both exist as concepts.

Fifth - don’t we need to make a distinction here: unicorns exist as a concept but unicorns don’t exist.

dancing - I don’t think the word ‘exist’ only covers physical substance. For example, in maths, we talk about proving the existence of all kinds of things that are highly abstract. And surely it’s quite normal in everyday speech, eg “despite the difficulties, hope still exists in this community”

Sleep seems to exist for other people but for me it is an elusive, um, thing.

Do triangles exist, though? Do those chalky approximations on blackboards in a slightly non-Euclidian space exist in an ideal Platonic universe of perfect forms?

What about colours, sounds, smells? Do they exist? Dissect a brain and you won't find 'purpleness'.

I don't understand reality at all.

I said this is more of a question for Philosophers' Corner!

I see there is a Philosophy / Religion board but that seems preoccupied more with religion than questions of ontology - which suggest this migh be a better way to go --> en.wikipedia.org/wiki/Ontology