I would like to use the term "non pliable" in the claim preamble which does not appear in the specification. However the term "pliable" does appear in the specification but is not specifically defined.

1. A method for converting a non pliable widget into a pliable widget, the method comprising:
   compressing the widget;
   heating the widget;
   applying a force to the widget.


  1. How a term not present in the specification is interpreted when used in a preamble.

  2. Do the claim's steps define the meaning of the terms "non pliable" and "pliable" in the preamble?

  3. Can a claim be deemed indefinite because of use of a term in a preamble which is not present in specification?

  4. Howe likely it is that such claim will be invalidated in court during a potential patent challenge?

2 Answers 2

  1. Use of a term as a preamble when it is not present in the Description: a higher chance of an indefiniteness rejection. That is, can be used against you.
  2. If the claim's steps actually define the term you use in the preamble, lesser chance of an indefiniteness rejection.
  3. The term can be used in the preamble even if not present in the Speci as filed (that is, there is no such requirement as far as I know). Also, you can make an Amendment to the Description (to add/define the preamble term you want to add) without adding new matter- depends on the way you draft the amendment.
  4. This is a tricky one: varies from case to case. There are several case laws. See, for example: Patently-O 1 Patently-O 2 Patently-O 3 IPWatchDog 1 IPWatchDog 2 (although I wouldn't take the last one as a hard and fast rule)

Lack of a preamble: if prior art in the same field is not found, art from another field can still be used for a Novelty (102) rejection. Generally, if a preamble is present in a claim, and prior art from the same field as the Application is not found against the claim, an Obviousness Rejection (103) would be easier to apply than a 102. If you don't want to use a preamble, you could consider slipping the limitation "wherein the blah is used for converting a pliable widget into a widget that is not pliable" into the end of the claim, which will usually be given more weight (and therefore closer prior art being applied), with a reduced chance of an indefiniteness rejection.

  • This is great detailed answer. I marked it as default answer and upvoted.
    – Jimski
    Sep 4, 2019 at 18:46

It is best not to use terms in a claim that are not present in the specification however it will not necessarily be objected to as indefinite. I assume, in your example, that the specification does explain how a non-pliable widget is made into a pliable widget. If you also explain why one would want a pliable widget and what you can do with a pliable widget that you can't do with a non-pliable widget, then you have provided an operative definition of pliable.

Preambles are treated inconsistently in U.S. patent law. The shorthand is that they are not considered when it would benefit you but they are used when it hurts you. During examination an examiner will often say that the preamble is not taken as a limitation. During litigation, if someone is doing your same steps but can argue that they are not fulfilling your preamble, they might get away from infringing on your steps.

  • In short: don't.
    – user18033
    Aug 25, 2019 at 11:34

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