## mass density gradient, $$\bigtriangledown \rho$$, $$\text{grad}\: \rho$$

https://doi.org/10.1351/goldbook.M03715
Change in @M03714@ in a small distance divided by that distance.
Source:
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 980 [Terms] [Paper]