Patentability: The Adequate Description Requirement of 35 U.S.C. 112

EDITORIAL NOTE: This article on the description requirement is the final segment of our basic patentability overview series. To start reading from the beginning please see: Patentability Overview: When can an Invention be Patented? You can also jump to information on the novelty requirement or information on the law of obviousness.


Description requirementThe crux of this so-called adequate description requirement is that once the first four patentability requirements are satisfied the applicant still must describe the invention with enough particularity such that those skilled in the art will be able to make, use and understand the invention that was made by the inventor. For the most part this requirement can be explained as consisting of three major parts. First is the enablement requirement, next is the best mode requirement and finally is the written description requirement.

The enablement requirement requires the inventor to describe his or her invention in a manner that would allow others in the industry to make and use the invention. Enablement looks to placing the subject matter of the claims generally in the possession of the public.

The best mode requirement requires the inventor to disclose his or her preferred way of carrying out the invention at the time the patent application is filed. There is no requirement that the inventors preferred embodiment be updated as the patent application works its way through the PTO. Best mode looks to whether specific instrumentalities and techniques have been developed by the inventor and are known at the time of filing as the best way of carrying out the invention.


The enablement requirement, thus, looks to the objective knowledge of one of ordinary skill in the art, while the best mode inquiry is a subjective, factual one, looking to the state of the mind of the inventor.

The best mode requirement has now been eliminated from U.S. patent law for the most part.  The America Invents Act (AIA), which was signed into law on September 16, 2011, prohibits a claim from being found to be invalid as a result of failure to present the best mode.  In other words, during litigation (for example) a defendant cannot challenge a patent claim saying that the inventor failed to disclose the best mode.  The best mode requirement, however, continues to live.  35 USC 112(a) continues to require patent applications to contain the best mode of the invention, if in fact one exists.

Given that best mode cannot be used to invalidate a patent claim once it is obtained the best mode requirement is now viewed as a paper tiger.  Yes, it is required, but there is no penalty for the inventor or patent owner for failure to disclose the best mode as long as they do not get caught by the patent examiner. Getting caught by the patent examiner is highly unlikely since best mode is subjective and there is really no mechanism for the patent examiner ever to know what the inventor actually knows or believes. Still, the Patent Office has indicated that if a patent examiner stumbles across a best mode violation they will reject claims accordingly. Furthermore, if it really is a preference generally speaking you will want to disclose it so that what you prefer will be able to be claimed.

The third description requirement is the written description requirement, which is also found in 35 U.S.C. §112(a). The written description requirement is separate and distinct from the enablement requirement, although related in important ways. The written description requirement serves a teaching function, as a “quid pro quo” in which the public is given meaningful disclosure in exchange for being excluded from practicing the invention for a limited period of time.

Still confused as to what this means? If you are confused you are understanding well. To be sure, the definition of the written description requirement is quite elusive. For generations the written description requirement had been confined to making sure that what was originally filed in the patent application adequately defined the full parameters of the invention being claimed. Today, the written description requirement means much more, but the Federal Circuit has yet to be able to articulate the requirements in a truly easy to explain way.

Perhaps the key to understanding the difference between enablement and the written description requirement is that you can bootstrap knowledge of one of skill in the art into your application for enablement purposes, but no such bootstrapping is allowable under the written description requirement.  If you leave something out it is not a part of your written description even if someone of skill in the art would understand that you left something out. In this sense the written description requirement is a “four corners” requirement. What you include in your patent application defines the possible extent of the exclusive rights you will obtain, nothing more. Once it is known what is in the four corners of your patent application and, therefore, the invention that you actually possess, the law then turns to the enablement question and asks whether one of skill in the art would know how to make and use the invention. In this regard the written description requirement and the enablement requirement are similar and directly related, yet separate requirements.

The remaining elements of the adequate description requirement relate to claims. It is the claims that define the invention, so particular attention must be given to writing good, broad claims. Discussion of claims, however, goes well beyond the scope of this primer.  For discussion of patent claims see:

For more information on patent application drafting please see:


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One comment so far.

  • [Avatar for Paul F. Morgan]
    Paul F. Morgan
    June 25, 2017 11:35 am

    Good article.
    What is surprising is how infrequently “enablement” rejections or invalidity defense arguments get to the Fed. Cir. and get sustained by the Fed. Cir. in comparison to other issues.
    The “the written description” requirement can also be expressed as having in the specification at least some teaching of what is it that you think is your novel feature or combination? [Especially where attempted new claims differ significantly from any original claims.]