should there be a distinction between "more than you can afford to lose" and "an amount that you can afford to lose, but it's quite a large percentage of what you own"...?
Well yeah, there is a distinction. That's why you expressed it differently.
yes
..I feel the phrase gets thrown around a lot... personally more than I can afford to lose would mean I can't support myself if I lost it. I lost so much that I can't afford other things.
for someone else the same phrase will mean something different, e.g. if they lost their savings. They may still have their house and enough money coming in to survive and maintain a certain quality of life... the distinction is present but the phrase stays the same.
I'm enquiring more as to what a possible "standard definition" of the phrase should be.
e.g. I read some advice somewhere that it's not a good idea to have more than 5-10% of your assets in one investment. For those who subscribe to that practice, if they lost more than 11% then that would be their "more than they can afford".
EDIT - thanks for the other replies, typing rather slow today...
Rampion essentially covered what I've written here