1. [adj]  being of striking appropriateness and pertinence; "the successful copywriter is a master of apposite and evocative verbal images"; "an apt reply"
2. [adj]  mentally quick and resourceful; "an apt pupil"; "you are a clever man...you reason well and your wit is bold"-Bram Stoker

APT is a 3 letter word that starts with A.

1. \Apt\, a. [F. apte, L. aptus, fr. obsolete apere to fasten,
   to join, to fit, akin to apisci to reach, attain: cf. Gr. ?
   to fasten, Skr. [=a]pta fit, fr. [=a]p to reach attain.]
   1. Fit or fitted; suited; suitable; appropriate.
            They have always apt instruments.     --Burke.
            A river . . . apt to be forded by a lamb. --Jer.
                                                  Taylor.
   2. Having an habitual tendency; habitually liable or likely;
      -- used of things.
            My vines and peaches . . . were apt to have a soot
            or smuttiness upon their leaves and fruit. --Temple.
            This tree, if unprotected, is apt to be stripped of
            the leaves by a leaf-cutting ant.     --Lubbock.
   3. Inclined; disposed customarily; given; ready; -- used of
      persons.
            Apter to give than thou wit be to ask. --Beau. & Fl.
            That lofty pity with which prosperous folk are apt
            to remember their grandfathers.       --F. Harrison.
   4. Ready; especially fitted or qualified (to do something);
      quick to learn; prompt; expert; as, a pupil apt to learn;
      an apt scholar. ``An apt wit.'' --Johnson.
            Live a thousand years, I shall not find myself so
            apt to die.                           --Shak.
            I find thee apt . . . Now, Hamlet, hear. --Shak.
   Syn: Fit; meet; suitable; qualified; inclined; disposed;
        liable; ready; quick; prompt.
   

2. \Apt\, v. t. [L. aptare. See {Aptate}.]
   To fit; to suit; to adapt. [Obs.] `` To apt their places.''
   --B. Jonson.
         That our speech be apted to edification. --Jer. Taylor.
   

1. automatically programmed tools.

2. audio processing technology.