A common approach to clarifying antecedent basis when there are multiple instances of some thing is to use ordinals: a first X, a second X, and so on.

Does appending prepositional phrases accomplish the same thing?

Example A:

  1. A system comprising a first X and a second X.
  2. The system of claim 1, wherein the first X is red.

Example B:

  1. A system comprising an X on the Y and an X under the Y.
  2. The system of claim 1, wherein the X on the Y is red.

Readability aside, is Example B a valid way to approach antecedent basis?

  • Are you asking whether example B is equivalent to example A? If so, the claim 1's don't seem to be equivalent to me, but I am not a lawyer.
    – Eric S
    Apr 21, 2023 at 15:59
  • I'm asking if Example B is valid.
    – jordanpg
    Apr 21, 2023 at 20:01
  • That's fine. I'm not a lawyer and always had a patent attorney draft my patents. It is just that stated "accomplish the same thing" in the question and to my reading the two claim 1's seem to be describing somewhat different things.
    – Eric S
    Apr 23, 2023 at 16:41

1 Answer 1


I think example B is valid. It is clear that there are (at least) two Xs and gives a way to refer to them.

However if the system sometimes swings around in operation and the “on Y” X ends up under Y or next to Y you will find it hard to write about the situation clearly. It also assumes the specification is clear about the spatial relationships.

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