principal

Principal \Prin"ci*pal\, n.
   1. A leader, chief, or head; one who takes the lead; one who
      acts independently, or who has controlling authority or
      influence; as, the principal of a faction, a school, a
      firm, etc.; -- distinguished from a subordinate,
      abettor, auxiliary, or assistant.
      [1913 Webster]

   2. Hence: (Law)
      (a) The chief actor in a crime, or an abettor who is
          present at it, -- as distinguished from an accessory.
      (b) A chief obligor, promisor, or debtor, -- as
          distinguished from a surety.
      (c) One who employs another to act for him, -- as
          distinguished from an agent. --Wharton. --Bouvier.
          --Burrill.
          [1913 Webster]

   3. A thing of chief or prime importance; something
      fundamental or especially conspicuous. Specifically:
      (a) (Com.) A capital sum of money, placed out at interest,
          due as a debt or used as a fund; -- so called in
          distinction from interest or profit.
      (b) (Arch. & Engin.) The construction which gives shape
          and strength to a roof, -- generally a truss of timber
          or iron, but there are roofs with stone principals.
          Also, loosely, the most important member of a piece of
          framing.
      (c) (Mus.) In English organs the chief open metallic stop,
          an octave above the open diapason. On the manual it is
          four feet long, on the pedal eight feet. In Germany
          this term corresponds to the English open diapason.
      (d) (O. Eng. Law) A heirloom; a mortuary. --Cowell.
      (e) pl. The first two long feathers of a hawk's wing.
          --Spenser. --J. H. Walsh.
      (f) One of turrets or pinnacles of waxwork and tapers with
          which the posts and center of a funeral hearse were
          formerly crowned. --Oxf. Gloss.
      (g) A principal or essential point or rule; a principle.
          [Obs.]
          [1913 Webster]See also:
subordinate abettor auxiliary assistant 

Principal \Prin"ci*pal\, a. [F., from L. principalis. See
   Prince.]
   1. Highest in rank, authority, character, importance, or
      degree; most considerable or important; chief; main; as,
      the principal officers of a Government; the principal men
      of a state; the principal productions of a country; the
      principal arguments in a case.
      [1913 Webster]

            Wisdom is the principal thing.        --Prov. iv. 7.
      [1913 Webster]

   2. Of or pertaining to a prince; princely. [A Latinism]
      [Obs.] --Spenser.
      [1913 Webster]

   Principal axis. See Axis of a curve, under Axis.

   Principal axes of a quadric (Geom.), three lines in which
      the principal planes of the solid intersect two and two,
      as in an ellipsoid.

   Principal challenge. (Law) See under Challenge.

   Principal plane. See Plane of projection
      (a), under Plane.

   Principal of a quadric (Geom.), three planes each of which
      is at right angles to the other two, and bisects all
      chords of the quadric perpendicular to the plane, as in an
      ellipsoid.

   Principal point (Persp.), the projection of the point of
      sight upon the plane of projection.

   Principal ray (Persp.), the line drawn through the point of
      sight perpendicular to the perspective plane.

   Principal section (Crystallog.), a plane passing through
      the optical axis of a crystal.
      [1913 Webster]See also:
Prince Principal axis Axis of a curve Axis Principal axes of a quadric Principal challenge 
Challenge Principal plane Plane of projection Plane Principal of a quadric 
Principal point Principal ray Principal section