'Principal plane' definitions:

Definition of 'Principal plane'

From: GCIDE
  • 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]