Inventive step

One of the criteria of patentability also called non-obviousness (see below). For the purposes of written opinions of the International Searching Authority and international preliminary reports on patentability (Chapter II of the PCT), a claimed invention shall be considered to involve an inventive step (to be non-obvious) if, having regard to the prior art as defined in the Regulations, it is not, at the prescribed relevant date, obvious to a person skilled in the art.
  

Inventive step (also called non-obviousness) is one of the criteria of patentability. A claimed invention shall be considered to involve an inventive step if the claimed invention is not obvious (to a person skilled in the relevant technology area) when compared to the prior art (technology) at the date of filing.