Nabla symbol
∇ The nabla symbol The nabla is a triangular symbol resembling an inverted Greek delta: or ∇. The name comes, by reason of the symbol's shape, from the Hellenistic Greek word for a Phoenician harp, and was suggested by the encyclopedist William Robertson Smith to Peter Guthrie Tait in correspondence. The nabla symbol is available in standard HTML as &nabla; and in LaTeX as \nabla. In Unicode, it is the character at code point U+2207, or 8711 in decimal notation, in the Mathematical Operators block. It is also called del. History The differential operator given in Cartesian coordinates on three-dimensional Euclidean space by was introduced in 1837 by the Irish mathematician and physicist William Rowan Hamilton, who called it ◁. (The unit vectors were originally right versors in Hamilton's quaternions.) The mathematics of ∇ received its full exposition at the hands of P. G. Tait. After receiving Smith's suggestion, Tait and James Clerk Maxwell referred to the operator as nabla in their extensive private correspondence; most of these references are of a humorous character. C. G. Knott's Life and Scientific Work of Peter Guthrie Tait (p. 145): It was probably this reluctance on the part of Maxwell to use the