facultative

1. Of or relating to faculty, especially to mental faculty.

   fähig

   of or relating to the mental faculties

2. Not obligate; optional, discretionary or elective.

   fakultativ, optional

   необяза́тельныйneobjazátelʹnyj, факультати́вныйfakulʹtatívnyj

   необов'язко́вийneobovʺjazkóvyj

   optional

3. That grants permission or power to do something.

   freigestellt

   granting a privilege or permission or power to do or not do something

4. Able to perform a particular life function, or to live generally, in more than one way.

   facultative feeder

   able to exist under more than one set of conditions

5. At which a given function is positive.

regular