right-hand screw rule
razan-e pic-e rast-gard
Fr.: règle de la vis droite
A rule that gives the direction of the resultant vector in a → vector product: A x B = C. It is the direction of advance of a right-hand screw whose axis, held perpendicular to the plane of A and B, is rotated in the same sense that rotates the first-named vector (A) into the second-named vector B through the smaller angle.
A piece of metal, consisting of a threaded and usually tapered shank that has a slotted head by which it is turned into something in order to fasten things together.
M.E. scrwe, screw, from M.Fr. escroue "nut, cylindrical socket," of uncertain origin.
Pic "screw," present stem of picidan "to twist, entwine, coil."