electron density function

The electron probability distribution function, ρ, defined as
ρ r = n ∫ Ψ * r 1 r 2 ... r n Ψ r 1 r 2 ... r n ⁢ d r 2 ... d 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 d r, i.e., electron density in this volume.
PAC, 1999, 71, 1919 (Glossary of terms used in theoretical organic chemistry) on page 1937