The Free On-line Dictionary of Computing (30 December 2018):

requirements

    The first stage of software development which
   defines what the potential users want the system to do.  In
   modern methods these requirements should be testable, and will
   usually be traceable in later development stages.  A common
   feature of nearly all software is that the requirements change
   during its lifetime.

   See software life-cycle.

   (1995-11-11)