An Etymological Dictionary of Astronomy and Astrophysics

1. Conforming to the usual standard, type, custom; not abnormal; regular; natural.
   2a) Math.: A perpendicular, particularly a line perpendicular to the tangent of a curve or curved surface at the point of contact of the tangent with the curve or the curved surface. See also → perpendicular; → vertical.
   2b) Optics: A line drawn perpendicular to the surface of a reflecting or refracting medium.

Etymology (EN): From L.L. normalis “standing at right angle, in conformity with rule,” from L. normalis “made according to a carpenter’s square,” from norma “rule, pattern,” literally “carpenter’s square.”

Etymology (PE): Hanjârvar, hanjârmand, adjectives of hanjâr, → norm.