English: Diagram illustrating the definition of the divergence of a vector field F at a point x. It shows a sequence of concentric closed surfaces S_i with volume V_i enclosing x. The red arrows represent the flux of the vector field ${\displaystyle \iint _{S_{i}}\mathbf {F} \cdot \mathbf {\hat {n}} \,dS,}$ through ${\displaystyle S_{i}}$. The divergence is the limit of the ratio ${\displaystyle S_{i}/V_{i}}$ as the volume shrinks to zero.