Rule of three (writing)

The rule of three, law of three, or power of three is a writing principle that suggests that things that come in threes are funnier, more satisfying, or more effective than other numbers of things. The reader or audience of this form of text is also thereby more likely to remember the information. This is because having three entities combines both brevity and rhythm with having the smallest amount of information to create a pattern. It makes the author or speaker appear knowledgeable while being both simple and catchy.

Slogans, film titles and a variety of other things have been structured in threes, a tradition that grew out of oral storytelling. Examples include the Three Little Pigs, Three Billy Goats Gruff, and the Three Musketeers. Similarly, adjectives are often grouped in threes to emphasize an idea.

The Latin phrase "omne trium perfectum" (everything that comes in threes is perfect, or, every set of three is complete) conveys the same idea as the rule of three.

The rule of three can refer to a collection of three words, phrases, sentences, lines, paragraphs/stanzas, chapters/sections of writing and even whole books. The three elements together are known as a triad. The technique may be used not just in prose but poetry, oral storytelling, films and advertising. In photography the rule of thirds produces a similar effect by dividing an image into three vertically and horizontally.

A tricolon is a more specific use of the rule of three where three words or phrases are equal in length and grammatical form.

A hendiatris is a figure of speech where three successive words are used to express a single central idea. As a slogan or motto, this is known as a tripartite motto.

Many advertising campaigns and public information slogans use the technique to create a catchy, memorable way of displaying information. In marketing theory, American advertising and sales pioneer St. Elmo Lewis laid out his three chief copywriting principles, which he felt were crucial for effective advertising:

"The mission of an advertisement is to attract a reader, so that he will look at the advertisement and start to read it; then to interest him, so that he will continue to read it; then to convince him, so that when he has read it he will believe it. If an advertisement contains these three qualities of success, it is a successful advertisement."

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