PRINTING n.
The act, art, or practice of impressing letters, characters, or figures on paper, cloth, or other material; the business of a printer, including typesetting and presswork, with their adjuncts; typography; also, the act of producing photographic prints. Block printing. See under Block. -- Printing frame (Photog.), a sh…
PYRAMIDAL a.
Same as Tetragonal. Pyramidal numbers (Math.), certain series of figurate numbers expressing the number of balls or points that may be arranged in the form of pyramids. Thus 1, 4, 10, 20, 35, etc., are trangular pyramidal numbers; and 1, 5, 14, 30, 55, etc., are square pyramidal numbers.
RATIONAL a.
Expressing the type, structure, relations, and reactions of a compound; graphic; -- said of formulæ. See under Formula. Rational horizon. (Astron.) See Horizon, 2 (b). -- Rational quantity (Alg. ), one that can be expressed without the use of a radical sign, or in extract parts of unity; -- opposed to irrational or ra…