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.
I think you summed it up pretty well right here. Ultimately, since a story is (in its most basic form) about a character trying to achieve a goal, the climax is the moment when she or he comes face-to-face with the opposition and finally has to do something about it. There's no easy out this time, like there may have been in earlier scenes. There's no compromise this time. There's no time left. The character has to make a decision, now, and that decision will affect the outcome of the story. It will affect whether or not the character satisfies her or his primary goal. And that decision, as you said, will show how that character has traversed her or his arc throughout the story. I think, by definition, it will have the highest amount of tension because everything is at stake. If the character makes the wrong decision, fails to act in time, etc, she stands to lose the goal forever. If she does act in time, make the right decision, etc, then, essentially, she accomplishes her goal and "wins." Though it may not be as obvious and clear-cut in the actual narrative, that's the general idea.
For me, defining the climax means acknowledging that it's dependent on what comes before it. So a lot depends on how the reader interprets the beginning of the piece (and perhaps also the ending). I think the climax occurs when there's some sort of disruption in the story; it shifts the original focus in some way (for example, there could be some sort of role reversal). A lot of times this will happen when the tension peaks, but like you, I don't think this simple definition is adequate; in fact, I would argue that the definition is outdated and too restrictive. As an example, you can see where this simple definition of the climax fails if you look at Chekhov's story stories. Often times he will end the story just before the moment of greatest tension. By doing this, I argue that he's making a point about conflict being continuous (i.e., there's always tension in the background; it's not concentrated at a certain point in the piece). However, his stories do change gears at some point, which is consistent with my definition of a climax.
Here's how I've always seen it: The climax is the point of no return. The protagonist can't back out, it's too late for them. If they back out, then everything they've fought for would be for naught. It's like Harry backing out on getting the Stone when he knew exactly what was about to happen. Or Frodo and Sam in Mordor, or in any historical war story when opposing sides are fighting a pitched battle that would decide the fate of the story (and to a larger extent, whatever they're fighting for.) The climax is when there's no turning back. I'm reminded of an example my creative writing teacher always used. In The Wizard of Oz, the climax was when Dorothy's last ditch attempt to return to Kansas fails. The balloon takes the wizard/little stage man away, leaving her and her dog behind. At that moment, she must decide what to do. Does she try to find some other way to get back to Kansas, or does she accept she'll never go home and try to start a new life in Oz? Climaxes aren't always when the protagonist is battling the antagonist (which is why the 'fight' with the Wicked Witch of the West doesn't really count as a climax, far as my creative writing teacher was concerned. Remember, Dorothy's entire quest was to get home to Kansas, not to kill a witch.) Sometimes it's personal, as in the case with Dorothy. Hope that helps!
It's a crescendo. It's what the action is working towards. Some have eluded to its sexual meaning, which is pretty much spot one. But if that's not clearing it up, think of a piece of classical music. The Borero, is a good example, which was made 'popular' by Torvil and Dean, the figure skaters. The music starts low and, gentle, then begins to grow louder and more intense (the passion intensifies or the action grows) until it is so intense, so overwhelming there is only one way to go.......the climax! Here's a link to the music and the skaters:
I'm voting for those definitions that emphasise the moment the story is working towards. Sometimes the main character/s are not even making a big decision themselves about the antagonist or anything: but are just being acted upon. EG: To kill a Mockingbird. Scout and Gem are attacked by the drunk on the way home from the pageant, but saved by Boo Radley. All the themes came together and unfolded. However, emotionally the climax of the movie for me was Atticus's summary speech in court. I made a fool of myself in creative writing class just last week suggesting that was the climax of the story, but of course it was just a really moving part of the story where all kinds of prejudice and racism is named and shamed. The court case is not even the climax of the plot: just a device heading towards the climax.
