Final answer:
Unity of time, place, and action are collectively referred to as the 'three unities' in the context of Greek and Roman tragedy.
Step-by-step explanation:
Unity of time, unity of place, and unity of action are called the three unities, all taken from Greek and Roman literary style. These principles were applied, especially in the genre of tragedy, to create a dramatic structure that mimics the natural cohesiveness and limits of real-life situations. The unity of action meant that the play should have one main action or plot; the unity of time suggested that the action should take place within a span no longer than a single day; and the unity of place dictated that the action should occur in one location. These rules were notably formulated in the context of Greek tragedy, wherein they served as guidelines to ensure the play's coherence and intensity.