An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A vector → operator which is the vector product of the → del operator with a vector function. For a three-dimensional function, it is equal to the sum of the vector products of the unit vectors and → partial derivatives in each of the component directions: ∇ x F(x,y,z) = (∂F_z/∂y - ∂F_y/∂z)i + (∂F_x/∂z - ∂F_z/∂x)j + (∂F_y/∂x - ∂F_x/∂y)k. The curl of a vector field is a vector field. ∇ x F is sometimes called the rotation of F and written rot F.

Metathesis of crulle "curly," probably from an unrecorded O.E. word or from M.Du. krul "curly."

Tâv, variants tow, tâb "twist, swing," from tâbidan "to spin, to twist."