Del, or nabla, is an operator used in mathematics as a vector differential operator, usually represented by ∇. When applied to a function defined on a one-dimensional domain, it denotes the standard derivative of the function as defined in calculus. When applied to a field, it may denote any one of three operations depending on the way it is applied: the gradient or (locally) steepest slope of a scalar field ; the divergence of a vector field; or the curl (rotation) of a vector field.