https://doi.org/10.1351/goldbook.ET07024

The electron probability distribution function, ρ, defined as \[\rho (\mathbf{r}) = n\ \int \Psi ^{\text{*}}\left[\mathbf{r}(1),\mathbf{r}(2)\,\text{...}\,\mathbf{r}(n)\right]\ \Psi \left[\mathbf{r}(1),\mathbf{r}(2)\,\text{...}\,\mathbf{r}(n)\right]\text{d}\mathbf{r}(2)\,\text{...}\,\text{d}\mathbf{r}(n)\] where Ψ is an electronic wave-function and integration is made over the coordinates of all but the first electron of n. The physical interpretation of the electron density function is that ρ d r gives the probability of finding an electron in a volume element dr, *i.e*., electron density in this volume.*Source: *

PAC, 1999,*71*, 1919. 'Glossary of terms used in theoretical organic chemistry' on page 1937 (https://doi.org/10.1351/pac199971101919)

PAC, 1999,