Industrial applicability is defined in PCT Article 33(4).
PCT Article 33.
The International Preliminary Examination
- (4) For the purposes of the international preliminary examination, a claimed invention shall be considered industrially applicable if, according to its nature, it can be made or used (in the technological sense) in any kind of industry. “Industry” shall be understood in its broadest sense, as in the Paris Convention for the Protection of Industrial Property.
The above provisions apply mutatis mutandis to the written opinion of the International Searching Authority. See PCT Rule 43bis.1(b).