Patents are products of the legal system.
As such, they apply only to inventions, and then only if the invention falls within legally-defined categories. Anything outside these categories cannot be patented. Granted to inventions that involve a new and useful process, device, machine, manufactured item, or chemical compound or formula. Utility patents, which apply to virtually anything that can be made, are granted for a 20-year period, after which the invention becomes public property. Granted to a new, original or ornamental design for a manufactured item.