What are the four purposes of 35 U.S.C. 101?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

According to MPEP 2107.01, 35 U.S.C. 101 has been interpreted as imposing four purposes:

• Limiting an inventor to ONE patent for a claimed invention
• Requiring proper inventorship
• Defining which categories of inventions are eligible for patent protection
• Ensuring that patents are granted only on inventions that are “useful”

The MPEP states: “35 U.S.C. 101 has been interpreted as imposing four purposes. First, 35 U.S.C. 101 limits an inventor to ONE patent for a claimed invention. […] Second, the inventor(s) must be the applicant in an application filed before September 16, 2012, […] and the inventor or each joint inventor must be identified in an application filed on or after September 16, 2012. […] Third, 35 U.S.C. 101 defines which categories of inventions are eligible for patent protection. […] Fourth, 35 U.S.C. 101 serves to ensure that patents are granted on only those inventions that are “useful.””