The 3 act structure for screenplays is used in virtually every screenplay today. A screenplay does not necessarily have to have 3 acts.  Even more important than implementing this widely accepted structure, screenwriting that maintains the reader and viewer’s interest is the true goal.  To do this, screenwriters need to understand how scenes link together. Most screenplays are said to have 3 acts because they pose a question, deliberate on the answer, and finally give the answer.  This structure can be used in many ways based on the writer’s creativity.  The most important part is to keep the reader’s interest.  Once you write from this perspective, the structure will follow naturally. Nevertheless, the 3 act structure is the most widely recognized and accepted structure.  As such, deviating from the structure is not recommended unless the writer has a clear sense and purpose for the change.