Plot is a narrative (and, traditionally, literary) term defined as the events that make up a story, particularly: as they relate to one another in a pattern or in a sequence; as they relate to each other through cause and effect; how the reader views the story; or simply by coincidence.
A plot was defined in 1927 by the English novelist E. M. Forster. Forster defined a plot as the cause‐and‐effect relationship between events in a story.
It was under these circumstances that, a plot is used to design a story. In screenwriting, the treatment contains the plot, and provides the fundamentals for the screenplay. It is a prose, but has not yet divided into scenes (as contrasted with the outline makes a few line summary of each scene). In addition, more than a few writers employ dozens of index cards.
Generally, screenwriters combine plot with plot structure into treatment, then, this structure is referred to as the Three act structure. This structure divided the length of a film into three parts, namely, three acts. Their acts have each function of Set-up, Confrontation, and Resolution. Each act is connected by two Plot points (i.e., turning points), which Plot point I is Act I border with Act II, then, Plot point II is also similar. Syd Field, United States screenwriter, redefined the three act structure in that way, for a film analysis in 1979.
As a screenwriter, I always focus on plot before characters and dialogue. It’s the most important piece.