We define the vector矢量 that represents both the magnitude,大小and the direction方向 of the maximum space rate最大空间变化率of Increase增加 of a scalar as the gradient梯度 of that scalar. We define the divergence of a vector field a at a point, abbreviated(A 写)divA, as the net outward flux(静通量) of a per unit volume as the volume about the point tends to zero. The curl of a vector field a, denoted by curl a or VxA, is a vector whose magnitude is the maximum net circulation最大净环量 of A per unit area as the area tends to zero g and whose direction is the normal direction of the area when the area is oriented to make the net circulation maximum.矢量场A的旋度是一个矢量,其大小为 当面积趋于零时单位面积上A的最大净环量,其方向为当 面积的取向使得净环量呈最大时,该面积的法线方向。The curl of a vector field A, denoted by curl A or A, is a vector whose magnitude is the maximum net circulation最大净环量 of A per unit area as the area tends to zero零 and whose direction is the normal direction of the area when the area is oriented to make the net circulation maximum. 矢量场A的旋度是一个矢量，其大小为 当面积趋于零时单位面积上A的最大净环量，其方向为当 面积的取向使得净环量呈最大时，该面积的法线方向。 We define the vector矢量 that represents both the magnitude大小 and the direction方向 of the maximum space rate最大空间变化率 of increase增加of a scalaras the gradient梯度of that scalar. We define the divergence of a vector field A at a point, abbreviated(简 写） div A, as the net outward flux（静通量） of A per unit volume as the volume aboutthe pointtends to zero