The older among us have “unlearned” the prohibition of the word “or” in patent claims, and have reasoned that if “or” is acceptable, its cousin “and/or” is acceptable in patent claims as well.  A few years ago, the USPTO confirmed this in Ex Parte Gross, App. 11/565/441, (PTAB 2014).  Mr. Gross claimed:

forming a website collective whose members include a plurality of different websites characterized by a common parameter including at least one of a common content topic, and/or a common contractual arrangement.

The Examiner took exception to “and/or” rejecting the claim as indefinite.  The Board of Appeals reversed the Examiner, agreeing with Mr. Gross that “‘and/or’ covers embodiments having element A alone, element B alone, or elements A and B taken together.”  The Board did add that the preferred verbiage” would be “at least one of A and B” and not “at least one of A an/or B.”

Thus “and/or” in a claim is not necessarily indefinite, but it is not the preferred way to write a claim.