As another commenter pointed out, > One plausible definition is “system deviates from its specification” And that's quite reasonable. So I actually retract my

As another commenter pointed out, > One plausible definition is “system deviates from its specification” And that's quite reasonable. So I actually retract my argument. For my own definition, I was considering a bug to be any behavior that the software engineers weren't expecting. Because those can exist invisibly for a long time until they become so bad they become visible. They can also exist for decades without causing any problems to functionality at all.