Narrative cut between scene blocks — divides story into acts and creates tension points for commercial breaks or dramatic pause. TV structure, used in cinema too.
An act break divides a story into dramatically meaningful blocks — not just where a scene ends, but where maximum tension has been built and the viewer is on the edge of their seat. On television, this is brutally practical: you need breaks for commercials, but you can't place them in the middle of a confrontation. The professional solution is: the end of the first act must be so strong that viewers return after the commercial break. You won't notice any of this on set — it's purely editing and dramaturgy work. But during production, you should keep in mind where these break points lie, especially for series.
Structurally, it works like this: you typically have three to five acts (depending on the format). Each act builds on the previous one and ends with a turning point — a piece of information, a twist, an escalation that forces the audience to keep watching. An action film might end after the first act with an explosion. A crime drama with a shocking discovery. The length isn't sacred — 12 minutes for a TV episode, 25 minutes for a feature, but it's about dramatic logic, not the clock.
In the edit, this is your architecture. You know during editing: here the music needs to swell, here a cut needs to be sharp to emphasize the pivot. A cut immediately after the cliffhanger is more impactful than a gentle dissolve. Some editors also insert a beat of silence — that microsecond of air between two scenes can build more tension than any music. In streaming series, the act structure is almost perfectly mechanical: the end of an episode is the end of an act, the next episode is the resolution plus new setup.
The most common mistake: placing an act break too weakly. If you don't feel why the story *must* pause here, then it's in the wrong place. Also, no break in the middle of emotional resolution — that's frustrating. The best placement comes from screening: watch your rough cut, and you'll feel where air naturally emerges. That's where the break belongs.