Enablement:The requirement that a patent application must contain a description sufficient to enable a person skilled in the art to make and use the invention without undue experimentation.
Written Description:The requirement that a patent application must contain a written description of the invention that shows the inventor had possession of the claimed invention at the time of filing.
Patentable Subject Matter: The requirement that an invention must fall into one of the categories of patentable subject matter, such as a process, machine, manufacture, or composition of matter.