The tragic turning point where irreversible harm or downfall occurs — protagonist's fate sealed. Classical term for the moment before resolution.
The catastrophe is the point of no return for your protagonist. Not the explosion, not the accident—but the dramaturgical moment where the consequences of their actions or character manifest irreversibly. You recognize it because from this point on, any further action only accelerates or delays the inevitable, but can no longer avert it.
In the classic three-act structure, the catastrophe occurs at the end of the second act or early in the third—where the exposition and rising action lead to their logical, destructive consequence. The key distinction: it is not identical to the climax. The catastrophe is the point of decision; the climax is the confrontation with it. In a heist film, the catastrophe might be that the police have figured out the plan; the climax is the subsequent car chase or hide-and-seek. The story now knows how it will end—your audience does not yet.
Practically on set and in the edit: you signal the catastrophe through a structural cut. The rhythm changes, the music starts differently (or drops out), the lighting becomes harsher or more isolated. It's as if the world around your character suddenly shrinks. Not visually louder, but more precise. A phone call instead of a scene. A quiet moment instead of a dramatic outburst. The best catastrophe often feels anticlimactic—because it simply removes the illusion of control.
Be careful not to confuse it with the peripeteia (the turning point), which can also bring good fortune. The catastrophe is specific: it shatters hope. It makes the path to resolution unavoidable. That's why it also works emotionally—your audience feels not shock, but fatalism. That is the power of this structure.