An Etymological Dictionary of Astronomy and Astrophysics

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.

Etymology (EN): Metathesis of crulle “curly,” probably from an unrecorded O.E. word or from M.Du. krul “curly.”

Etymology (PE): Tâv, variants tow, tâb “twist, swing,” from tâbidan “to spin, to twist.”