Ordinary Skill v Skilled in the Art

So, you’ve probably seen the phrase “one of ordinary skill in the art” and the phrase “one skilled in the art”. So, what’s the difference?
Well, there are several and we’ll start with what each is used for.

“one of ordinary skill in the art”
        For patentability, that is passing or overcoming a 102 (novelty) or 103 (obvious) rejection the standard is “one of ordinary skill in the art”. For example, 35 USC § 102 has “a person of ordinary skill in the art must have been enabled to make the invention without undue experimentation”, “compliance with the “how to make” requirement is judged from the viewpoint of a person of ordinary skill in the art”, “a disclosure may be cited for all that it would reasonably have made known to a person of ordinary skill in the art”.
In fact, the MPEP has section 2141.03 Level of Ordinary Skill in the Art where they discuss on of ordinary skill in the art.
Please realize that this standard is AT the time the application was filed, NOT afterwards.

§ 103. Conditions for patentability; non-obvious subject matter specifically states:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.

Please realize that the inventor is not considered a person of ordinary skill because they have invented something, so they are highly skilled.

“one skilled in the art”
35 U.S.C. § 112 Specification specifically states:
(a) IN GENERAL.—The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected…