di·rec·tion·al /-ʃnəl, ʃənḷ/
  (a.)方向的
  directional
  方向 定向 向
  directional
       adj 1: relating to or indicating directions in space; "a
              directional microphone" [ant: omnidirectional]
       2: relating to direction toward a (nonspatial) goal; "he tried
          to explain the directional trends of modern science"
       3: showing the way by conducting or leading; imposing direction
          on; "felt his mother's directing arm around him"; "the
          directional role of science on industrial progress" [syn:
          directing, directive, guiding]