Functionality doctrine

In United States trademark law, the functionality doctrine prevents manufacturers from protecting specific features of a product by means of trademark law. This separates trademarks from patents — trademarks serve to protect a firm's reputation and goodwill, whereas patents serve to protect processes, machines, and material inventions.

If a feature gives a producer a competitive advantage which is not related entirely to its function as a brand identifier, then it cannot be trademarked. The rationale behind this doctine is that product markets wouldn’t be truly competitive if newcomers couldn’t make product with a feature that consumers demand.