Mathematics and Physics Glossary

Nadir, n. (Astron.) A point on the celestial sphere directly below the observer, diametrically opposite the zenith.

-- Nadir of the sun (Astron.), the axis of the conical shadow projected by the earth. Crabb.

Napierian logarithm, n. [Invented by John Napier.] (Math.) See Natural logarithm.

Napier's bones, n.pl. (Math.) A set of graduated rods used to perform multiplication quickly.

Nappe n. (Geom.) Sheet; surface; all that portion of a surface that is continuous in such a way that it is possible to pass from any one point of the portion to any other point of the portion without leaving the surface. Thus, some hyperboloids have one nappe, and some have two.

Natural, a. (Math.) Belonging to, to be taken in, or referred to, some system, in which the base is 1; said or certain functions or numbers; as, natural numbers, those commencing at 1; natural sines, cosines, etc., those taken in arcs whose radii are 1.

Natural logarithm, n. (Math.) A logarithm in which the base is the irrational number e (approx. 2.71828). For example, ln 10 = log_e 10 = 2.30258. Also called Napierian logarithm.