A more thorough explanation:

A substantial new question of patentability is a legal term used in patents. It refers to a threshold that must be met before the Commissioner for Patents can order a reexamination of a patent's validity. The U.S. Patent and Trademark Office cannot reopen an examination based solely on prior art and issues that arose during the original examination.

One example of a substantial new question of patentability could be if new evidence is discovered that was not considered during the original examination. For instance, if a company discovers a prior art that was not previously known, they can request a reexamination of the patent's validity.

Another example could be if there is a change in the law that affects the patent's validity. For example, if a new court ruling is made that affects the interpretation of a patent's claims, this could be considered a substantial new question of patentability.

These examples illustrate how a substantial new question of patentability requires more than just a simple challenge to a patent's validity. It must be a significant issue that was not previously considered and has the potential to affect the patent's validity.