Short for the gradient of a quantity. In an orthogonal coordinate system with coordinates {u_{1},u_{2},u_{3}}, where a line element *ds* is given by

ds²=h_{1}² du_{1}² + h_{2}² du_{2}² + h_{3}² du_{3}²

then the gradient of a

scalar quantity φ is given by

grad φ = (1/h_{1})(δ φ/δ u_{1}) **i**_{1} + (1/h_{2})(δ φ/δ u_{2}) **i**_{2} +(1/h_{3})(δ φ/δ u_{3}) **i**_{3}

where

**i** is the

unit vector
In cartesian coordinates

{u_{1},u_{2},u_{3}} = {x,y,z}

{h_{1},h_{2},h_{3}} = {1,1,1}

'Grad' is usually represented by an triangle 'pointing' downwards

See also div.