Rule of three (writing)
The rule of three is a writing principle which suggests that a trio of entities such as examples, events, or characters is more satisfying, effective, or humorous than other numbers, hence also more memorable, because it combines both brevity and rhythm with the smallest amount of information needed to create a pattern. Slogans, film titles, and a variety of other things have been structured in threes, a tradition that grew out of oral storytelling and continues in narrative fiction.