PLANE (3)

Plane, n. [[F. plane, L. plana. See Plane, v. & a.]] 1. 1. (Geom.) A surface, real or imaginary, in which, if any two points are taken, the straight line which joins them lies wholly in that surface; or a surface, any section of which by a like surface is a straight line; a surface without curvature.
2. 2. (Astron.) An ideal surface, conceived as coinciding with, or containing, some designated astronomical line, circle, or other curve; as, the plane of an orbit; the plane of the ecliptic, or of the equator.
3. 3. (Mech.) A block or plate having a perfectly flat surface, used as a standard of flatness; a surface plate.
4. 4. (Joinery) A tool for smoothing boards or other surfaces of wood, for forming moldings, etc. It consists of a smooth-soled stock, usually of wood, from the under side or face of which projects slightly the steel cutting edge of a chisel, called the iron, which inclines backward, with an apperture in front for the escape of shavings; as, the jack plane; the smoothing plane; the molding plane, etc.
Objective plane (Surv.), the horizontal plane upon which the object which is to be delineated, or whose place is to be determined, is supposed to stand. — Perspective plane. See Perspective. — Plane at infinity (Geom.), a plane in which points infinitely distant are conceived as situated. — Plane iron, the cutting chisel of a joiner's plane. — Plane of polarization. (Opt.) See Polarization. — Plane of projection. (a) The plane on which the projection is made, corresponding to the perspective plane in perspective; — called also principal plane. (b) (Descriptive Geom.) One of the planes to which points are referred for the purpose of determining their relative position in space. — Plane of refraction or reflection (Opt.), the plane in which lie both the incident ray and the refracted or reflected ray.