Story equals problem.
Every story is about a problem that needs to be solved, and the protagonist is the only one who can do it. In short stories the problem is often the inciting incident. In longer fiction, the inciting incident typically leads to the problem. The inciting incident upsets the order of the fictional world and leads the protagonist toward the problem. No matter when the problem begins in the story (and it’s always in Act One) the problem needs to be weighty and vexing. It should also be personal, often creating a bond between the protagonist and antagonist. So a handy definition of plot is the constant struggle of the protagonist to solve an intolerable problem and reestablish order.