n.1. a slender tube of wood, metal, plastic, etc., containing a core or strip of graphite, a solid coloring material, or the like, used for writing or drawing.2. a stick of cosmetic coloring material for use on the eyebrows, eyelids, etc.3. anything shaped or used like a pencil, as a stick of medicated material: a styptic pencil.4. a narrow set of lines, light rays, or the like, diverging from or converging to a point: a pencil of sunlight.5. a slender, pointed piece of a substance used for marking.6. style or skill in drawing or delineation: He favored the late products of the artist's pencil.7. Math. the collection of lines, planes, or surfaces passing through a given point or set of points and satisfying a given equation or condition.8. Archaic. an artist's paintbrush, esp. for fine work.v.t.9. to write, draw, mark, or color with, or as if with, a pencil.10. to use a pencil on.11. pencil in, to schedule or list tentatively, as or as if by writing down in pencil rather than in ink: I'll pencil you in for ten o'clock.[1350-1400; ME pencel < MF pincel L penicillus painter's brush or pencil, dim. of peniculus little tail. See PENIS, -CULE1]
* * *▪ geometryin projective geometry, all the lines in a plane passing through a point, or in three dimensions, all the planes passing through a given line. This line is known as the axis of the pencil. In the duality of solid geometry, the duality being a kind of symmetry between points and planes, the dual of a pencil of planes consists of a line of points. In a plane, in which there is a duality between points and lines, the dual of a line of points is the pencil of lines through a point.▪ writing implementslender rod of a solid marking substance, such as graphite, enclosed in a cylinder of wood, metal, or plastic; used as an implement for writing, drawing, or marking. In 1565 the German-Swiss naturalist Conrad Gesner (Gesner, Conrad) first described a writing instrument in which graphite, then thought to be a type of lead, was inserted into a wooden holder. Gesner was the first to describe graphite as a separate mineral, and in 1779 the Swedish chemist Carl Wilhelm Scheele (Scheele, Carl Wilhelm) showed it to be a form of carbon. The name graphite is from the Greek graphein, “to write.” The modern lead pencil became possible when an unusually pure deposit of graphite was discovered in 1564 in Borrowdale, Cumberland, Eng.The hardness of writing pencils, which is related to the proportion of clay (used as a binder) to graphite in the lead, is usually designated by numbers from one, the softest, to four, the hardest. Artists' drawing pencils range in a hardness designation generally given from 8B, the softest, to F, the hardest. The designation of the hardness of drafting pencils ranges from HB, the softest, to 10H, the hardest.The darkness of a pencil mark depends on the number of small particles of graphite deposited by the pencil. The particles are equally black (though graphite is never truly black) regardless of the hardness of the lead; only the size and number of particles determine the apparent degree of blackness of the pencil mark. The degree of hardness of a lead is a measure of how much the lead resists abrasion by the fibres of the paper.
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