35 USC 101

MPEP Chapter 2100 covers the fundamental issues of patentability – what is patentable subject matter and how that matter must be expressed in an applicant’s disclosure. The Prometric Patent Bar tests MPEP 2100 heavily.

Note: MPEP 2100 also includes 35 USC 102 (a)-(g), 35 USC 103 and 35 USC 112, which are discussed in other posts under MyPatentBar’s Study Guide, PART 2.

What is patentable subject matter? Whoever invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent therefore, subject to the conditions and requirements of this title.” [35 USC 101]

To be patentable an invention must fall into one of the following statutory categories:
1) machine – e.g., new gizmo
2) manufacture (combination of materials) – e.g., new widget (gardening tool, computer chip)
3) composition of matter – e.g., new chemical composition or metal alloy
4) process (a new method for doing something) – note: special sub-category product by process

A claim cannot cite more than one of the statutory categories above (i.e., it is inappropriate to refer to a machine and composition of matter in the same claim).


  • Product: a new, useful and non-obvious machine, manufacture, or composition of matter (see statutory categories 1-3 above).
  • Process: a new, useful and non-obvious way of doing something, making something, or using something. A process may be patentable even though the resulting product itself is not.  Also, a process claim must include steps; it cannot claim the result without any steps (see comment below).
  • Product-by Process: patentability is based on the product, not the process. The patentability of a product does not depend on its method of production. If the product in the product-by-process claim is the same as or obvious over a product in the prior art, the claim is unpatentable even though the prior product was made by a different process.
    • Living subject matter is patentable: human intervention is necessary (e.g., genetically engineered material)
    • Also patentable are claims directed to a practical application of a natural phenomenon

    Not Patentable – examples

    • Naturally occurring living subject matter or raw materials
    • Inventions for which the broadest reasonable interpretation encompasses a human being
    • Mathematical, physical and natural laws
    • Processes that depend on natural laws, abstract ideas, etc. without some claimed practical application
    • Computer-related, descriptive material; this is copyrightable

    How that matter must be expressed in an applicant’s disclosure; Claim Interpretation

    • During examination, claims must be “given their broadest reasonable interpretation consistent with the specification.”
    • The words of the claim must be given their “plain meaning” unless they are defined in the specification.
    • The transitional phrases “comprising,” consisting essentially of,” and “consisting of” define the scope of a claim with respect to what unrecited additional components if steps, if any, are excluded from the scope of the claim. [MPEP 2111.03]
      • Comprising – non-exclusive language
      • Consisting essentially of – limiting language*
      • Consisting of – exclusive language*

      *revised from dk’s comment below