The U.S. Patent and Trademark Office (PTO) issues three different kinds of patents:
utility patents. Useful inventions may qualify for a utility patent if they fit into at least one of these five categories: a process, a machine, a manufacture, a composition of matter or an improvement of an existing idea that falls into one of these categories. Often, an invention that qualifies for a patent because of its usefulness will fall into more than one of the categories. For instance, computer software can usually be described both as a process (the steps that it takes to make the computer do something) and as a machine (a device that takes information from an input device and moves it to an output device). Regardless of the number of categories an invention falls under, only one utility patent may be issued on it.
design patents. To qualify for a patent under the design test, a design must be innovative, nonfunctional and part of a functional manufactured article. For example, a new shape for a car fender, bottle or flashlight that doesn’t improve its functionality would qualify.
plant patents. Patents may be issued for any asexually or sexually reproducible plants (such as flowers) that are both novel and nonobvious. Plant patents are the least frequently issued type of patent.
Related terms: combination patent; composition of matter; design patents; improvement inventions; machines as patentable subject matter; manufactures as patentable subject matter; new-use invention; non-statutory subject matter; operability; patentability; plant patents; processes (or methods) as patentable subject matter; public domain; public use; software patents; statutory bar; statutory subject matter; utility patents, defined.