It's really hard to formally define hallucination, for me it's a "know it when you see it" situation. In my view, saying "10 + 4 = 15" is not a hallucination b

It's really hard to formally define hallucination, for me it's a "know it when you see it" situation. In my view, saying "10 + 4 = 15" is not a hallucination but inventing a citation that doesn't exist is one. There is a big grey area between these, like what if it cites a real paper but gets the year wrong? Is that a hallucination (because the paper as cited is fake), or just an incorrect statement (because the year is just wrong)?