Pole of a lens

Pole Pole, n. [As. p[=a]l, L. palus, akin to pangere to make fast. Cf. {Pale} a stake, {Pact}.] 1. A long, slender piece of wood; a tall, slender piece of timber; the stem of a small tree whose branches have been removed; as, specifically: (a) A carriage pole, a wooden bar extending from the front axle of a carriage between the wheel horses, by which the carriage is guided and held back. (b) A flag pole, a pole on which a flag is supported. (c) A Maypole. See {Maypole}. (d) A barber's pole, a pole painted in stripes, used as a sign by barbers and hairdressers. (e) A pole on which climbing beans, hops, or other vines, are trained. [1913 Webster]

2. A measuring stick; also, a measure of length equal to 5? yards, or a square measure equal to 30? square yards; a rod; a perch. --Bacon. [1913 Webster]

{Pole bean} (Bot.), any kind of bean which is customarily trained on poles, as the scarlet runner or the Lima bean.

{Pole flounder} (Zo["o]l.), a large deep-water flounder ({Glyptocephalus cynoglossus}), native of the northern coasts of Europe and America, and much esteemed as a food fish; -- called also {craig flounder}, and {pole fluke}.

{Pole lathe}, a simple form of lathe, or a substitute for a lathe, in which the work is turned by means of a cord passing around it, one end being fastened to the treadle, and the other to an elastic pole above.

{Pole mast} (Naut.), a mast formed from a single piece or from a single tree.

{Pole of a lens} (Opt.), the point where the principal axis meets the surface.

{Pole plate} (Arch.), a horizontal timber resting on the tiebeams of a roof and receiving the ends of the rafters. It differs from the plate in not resting on the wall. [1913 Webster]