Neat question. Hotdogs are sandwiches imo.

That said, some types of investment provide additional advantages over simply appreciating in value. A stock can pay dividends, a house can be lived in, stuff like that. Could probably draw a distinction there. Additionally, some investments are guaranteed, like a savings bond. Could probably draw another there.

If I had to draw some clean line somewhere, I’d probably try define gambling as situations where you’re not intended to be able to “win money” on average, where investments are. The line is drawn via intention though, not anything quantitative. So, pretty inherently fuzzy.