Strictly when being used as a suffix for illness, sickness, disease, etc… Are they used for different things? Do they convey different nuances? Any insight would be greatly appreciated!
I’d recommend looking these up on Jisho, seeing what you get, and abstracting from there. Put an asterisk before each word (like *病 or *症) to see words that end in these kanji
After looking into it more, it looks like 病 is used when the cause is well understood/is the focus, while 症 is used elsewhere, i.e. that the symptom itself is the focus (source)
Thank you very much @snow-pine! I was also unaware of that little asterisk trick with Jisho, thank you for teaching me that!
Aye, an asterisk is one of the two wildcard searches in Jisho - it represents a space where any number of characters can go. The other wildcard search is ?, which represents a single character.
I think also 病 tends to relate to more body system or organ-specific diseases, whereas 症 is more symptom related, if that makes sense. So insomnia is more of a symptom, whereas lung disease is specific to a body system.
Edit: I just realised that @snow-pine has already said pretty much what I said but more succinctly!