Does the number of (embodiments) of a feature play a role? Let's consider a chair:

  1. The prior state is a three-legged chair. Is a chair with four legs patentable?
  2. The prior state is a four-legged chair. Is a chair with three legs patentable?

2 Answers 2


Since we all understand chairs, that example can be misleading. Yes, having more or fewer of some feature can make for a patentable claim. It can be tricky to write a claim for the fewer case. "A chair comprising three legs" also describes a chair with four legs. "A chair having exactly three legs" could be designed-around by having a vestigial fourth leg that had little cost or function.

You could draft a three or two legged chair claim as a "negative" limitation. "A chair not having more than two legs." Usually claims are about included elements, not excluded elements but negative limitations are allowed if the specification properly lays the ground work.

"Embodiment" would not be a clear term in the usage you are putting it to here.


In your example I'd say both 1 and 2 are not patentable since it would be obvious to someone skilled in making or designing chairs that you could make a chair with three or four legs. To be patentable an invention needs to be useful, novel and non-obvious. So if, for example a certain compound needs four chemicals to synthesize and you discover a process for making the same compound using only three chemicals it very likely could be patentable. If you discover a way to improve the compound by adding a fifth chemical that that too might be patentable. Obviousness is a tricky concept since many things seem obvious once they are invented. That said, if you find a way of making a chair with only two legs, that very well might be patentable.

  • Arguable. Consider that a chair with three legs will never have one leg that's too short (either because the chair or three floor is uneven). A three-legged chair would therefore be inventive in my opinion (in a fantasy world where chairs never had 3 legs nor is there any other hint to make them with less than 4 legs). I think that shows that it very much depends on the specific case. I'd say 5 legs might not be inventive because I don't see any credible technical effect.
    – user18033
    Aug 16, 2021 at 9:59
  • @DonQuiKong Actually, office desk chairs often have five casters. I think it’s because of greater stability and lower chance of tipping.
    – Eric S
    Aug 16, 2021 at 14:16
  • Then that's a good argument why five might also be inventive.
    – user18033
    Aug 16, 2021 at 14:43
  • @DonQuiKong The point I was trying to make was that just changing the number doesn't assure patentability, there has novel, non-obvious change. This was easier by providing a different example than a chair. Five caster desk chairs have been around for 50 years.
    – Eric S
    Aug 16, 2021 at 19:27
  • And you're right. But it's always a case by case thing
    – user18033
    Aug 17, 2021 at 18:47

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