In United States trademark law, the functionality doctrine prevents manufacturers from protecting specific features of a product by means of trademark law. There are two branches of the functionality doctrine: utilitarian functionality and aesthetic functionality. The rationale behind functionality doctrine is that product markets would not be truly competitive if newcomers could not make a product with a feature that consumers demand. Utilitarian functionality provides grounds to deny federal trademark protection to product features which do something useful. Patent law, not trademark, protects useful processes, machines, and material inventions. Patented designs are presumed to be functional until proven otherwise. Aesthetic functionality provides grounds to deny trademark protection to design features which are included to make the product more aesthetically appealing and commercially desirable. Aesthetic features are within the purview of copyright law, which provides protection to creative and original works of authorship.