Legal Definitions - idea–expression dichotomy

The idea-expression dichotomy is a fundamental principle in copyright law that distinguishes between an underlying concept or theme (the "idea") and the specific way that concept is presented or materialized (the "expression"). Copyright protection extends only to the unique expression of an idea, not to the idea itself.

This means that while you cannot copyright a general concept, you can copyright the particular words, images, sounds, or structure used to convey that concept. This distinction is crucial for encouraging creativity by allowing multiple creators to develop their own unique expressions of common ideas, without fear of infringing on another's basic concept.

Here are some examples to illustrate this principle:

• Example 1: A Story Plot

  The idea of a story about a detective solving a murder mystery in a secluded mansion is not copyrightable. This is a common plot device that many authors can use. However, the specific novel written by Agatha Christie, with its unique characters (e.g., Hercule Poirot), detailed plot twists, dialogue, setting descriptions, and narrative structure, constitutes her unique expression of that idea. Another author is free to write their own murder mystery in a mansion, but they cannot copy Christie's specific characters, dialogue, or detailed plot points without infringing on her copyright.

• Example 2: A Scientific Theory

  The idea of the theory of relativity, which describes how space and time are relative to the observer, is a scientific concept and cannot be copyrighted. It is a fundamental principle of physics. However, a specific textbook chapter, research paper, or documentary film that explains the theory of relativity using particular diagrams, unique analogies, specific wording, and a distinct organizational structure represents an author's or creator's unique expression of that theory. While anyone can teach or write about the theory of relativity, they cannot copy the exact text, illustrations, or unique presentation style from a copyrighted textbook without permission.

• Example 3: A Type of Game

  The idea of a board game where players buy, sell, and trade properties to build an empire and bankrupt opponents is not copyrightable. This is a general game concept. However, the specific game "Monopoly," with its unique board layout, specific property names (e.g., Boardwalk, Park Place), distinct game pieces, Chance and Community Chest cards, and detailed rules, is a protected expression of that idea. Other game designers are free to create their own property-trading games, but they cannot use the specific names, artwork, or exact rules from "Monopoly" without infringing on its copyright.