to turn on

Turn \Turn\ (t[^u]rn), v. i.
   1. To move round; to have a circular motion; to revolve
      entirely, repeatedly, or partially; to change position, so
      as to face differently; to whirl or wheel round; as, a
      wheel turns on its axis; a spindle turns on a pivot; a man
      turns on his heel.
      [1913 Webster]

            The gate . . . on golden hinges turning. --Milton.
      [1913 Webster]

   2. Hence, to revolve as if upon a point of support; to hinge;
      to depend; as, the decision turns on a single fact.
      [1913 Webster]

            Conditions of peace certainly turn upon events of
            war.                                  --Swift.
      [1913 Webster]

   3. To result or terminate; to come about; to eventuate; to
      issue.
      [1913 Webster]

            If we repent seriously, submit contentedly, and
            serve him faithfully, afflictions shall turn to our
            advantage.                            --Wake.
      [1913 Webster]

   4. To be deflected; to take a different direction or
      tendency; to be directed otherwise; to be differently
      applied; to be transferred; as, to turn from the road.
      [1913 Webster]

            Turn from thy fierce wrath.           --Ex. xxxii.
                                                  12.
      [1913 Webster]

            Turn ye, turn ye from your evil ways. --Ezek.
                                                  xxxiii. 11.
      [1913 Webster]

            The understanding turns inward on itself, and
            reflects on its own operations.       --Locke.
      [1913 Webster]

   5. To be changed, altered, or transformed; to become
      transmuted; also, to become by a change or changes; to
      grow; as, wood turns to stone; water turns to ice; one
      color turns to another; to turn Muslim.
      [1913 Webster]

            I hope you have no intent to turn husband. --Shak.
      [1913 Webster]

            Cygnets from gray turn white.         --Bacon.
      [1913 Webster]

   6. To undergo the process of turning on a lathe; as, ivory
      turns well.
      [1913 Webster]

   7. Specifically: 
      [1913 Webster]
      (a) To become acid; to sour; -- said of milk, ale, etc.
          [1913 Webster]
      (b) To become giddy; -- said of the head or brain.
          [1913 Webster]

                I'll look no more;
                Lest my brain turn.               --Shak.
          [1913 Webster]
      (c) To be nauseated; -- said of the stomach.
          [1913 Webster]
      (d) To become inclined in the other direction; -- said of
          scales.
          [1913 Webster]
      (e) To change from ebb to flow, or from flow to ebb; --
          said of the tide.
          [1913 Webster]
      (f) (Obstetrics) To bring down the feet of a child in the
          womb, in order to facilitate delivery.
          [1913 Webster]

   8. (Print.) To invert a type of the same thickness, as
      temporary substitute for any sort which is exhausted.
      [1913 Webster]

   {To turn about}, to face to another quarter; to turn around.
      

   {To turn again}, to come back after going; to return. --Shak.

   {To turn against}, to become unfriendly or hostile to.

   {To turn aside} or {To turn away}.
      (a) To turn from the direct course; to withdraw from a
          company; to deviate.
      (b) To depart; to remove.
      (c) To avert one's face.

   {To turn back}, to turn so as to go in an opposite direction;
      to retrace one's steps.

   {To turn in}.
      (a) To bend inward.
      (b) To enter for lodgings or entertainment.
      (c) To go to bed. [Colloq.]

   {To turn into}, to enter by making a turn; as, to turn into a
      side street.

   {To turn off}, to be diverted; to deviate from a course; as,
      the road turns off to the left.

   {To turn on} or {To turn upon}.
      (a) To turn against; to confront in hostility or anger.
      (b) To reply to or retort.
      (c) To depend on; as, the result turns on one condition.
          

   {To turn out}.
      (a) To move from its place, as a bone.
      (b) To bend or point outward; as, his toes turn out.
      (c) To rise from bed. [Colloq.]
      (d) To come abroad; to appear; as, not many turned out to
          the fire.
      (e) To prove in the result; to issue; to result; as, the
          crops turned out poorly.

   {To turn over}, to turn from side to side; to roll; to
      tumble.

   {To turn round}.
      (a) To change position so as to face in another direction.
      (b) To change one's opinion; to change from one view or
          party to another.

   {To turn to}, to apply one's self to; to have recourse to; to
      refer to. "Helvicus's tables may be turned to on all
      occasions." --Locke.

   {To turn to account}, {profit}, {advantage}, or the like, to
      be made profitable or advantageous; to become worth the
      while.

   {To turn under}, to bend, or be folded, downward or under.

   {To turn up}.
      (a) To bend, or be doubled, upward.
      (b) To appear; to come to light; to transpire; to occur;
          to happen.
          [1913 Webster]