What is essential material in patent applications?

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.

Essential material is defined in 37 CFR 1.57(d) as material that is necessary to:

• Provide a written description of the claimed invention as required by 35 U.S.C. 112(a)
• Describe the claimed invention in terms that particularly point out and distinctly claim the invention as required by 35 U.S.C. 112(b)
• Describe the structure, material, or acts that correspond to a claimed means or step for performing a specified function as required by 35 U.S.C. 112(f)

Essential material may only be incorporated by reference to a U.S. patent or patent application publication.