Of course, it sounds so easy to define, and we usually recognize it when we see it, but when you really start thinking about it, I don't think it is so easy to explain. I refuse to accept the answer of "It's the moment with the greatest tension" or anything like that. That's how it gets defined a lot in high schools etc, but I don't like it. It has to be the moment that the story has been building towards, of course, and it often has some sort of decision that the protagonist will make that will show how they've changed (or not changed) as a character, but realizing when you're writing exactly what the climax should be isn't always so simple as saying "oh, it will just be the moment of a the greatest amount of tension." Anyway, I just wanted to open it up for discussion and get some opinions.