\begin{definition}[Definition:Gradient Operator/Riemannian Manifold/Definition 2]
Let $\struct {M, g}$ be a Riemannian manifold equiped with a metric $g$.
Let $f \in \map {\CC^\infty} M : M \to \R$ be a smooth mapping on $M$.
The '''gradient''' of $f$ is the vector field obtained from the differential $\rd f$ obtained by raising an index:
:$\grad f := \paren {\rd f}^\sharp$
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\end{definition}