What is an inciting incident?
The inciting incident disturbs the character's existing situation and creates the problem, opportunity, danger, or invitation that begins the main story.
An inciting incident is the event or disruption that makes the story's central problem impossible for the protagonist to ignore.
The short definition
An inciting incident is the disruption that activates the central conflict. It can be an attack, discovery, arrival, loss, offer, accusation, meeting, mistake, or any event that changes what the protagonist must deal with.
It does not have to force immediate commitment. The protagonist may resist before making the larger decision that launches the next phase of the plot.
Inciting incident vs first plot point
They can be the same event, but they often are not. The inciting incident creates the problem; the first major plot point often represents the protagonist's commitment to dealing with it.
That distinction is useful when a story needs time for hesitation, investigation, preparation, or denial.
A useful test
Ask whether the main story could still unfold in roughly the same way if the event were removed. If yes, the event may not be the true inciting incident.
The strongest inciting incidents create consequences that make the old normal difficult to restore.
Put the idea to work in your draft
Good planning should reduce uncertainty and make the next writing decision easier. Use these steps to turn the ideas above into something concrete without adding unnecessary process.
Decide what this idea changes in your specific story before adding more detail.
Connect it to the chapter, character, event, plot point, or relationship it actually affects.
Write down the before-and-after state so the narrative consequence is easy to see during revision.
Use only as much structure as helps you make the next writing decision; stop before the planning becomes a second draft.