https://doi.org/10.1351/goldbook.15969
Quantity defining the permeability of molecules across a cell membrane and expressed as \[P = \frac{KD}{\Delta x}\] where \(K\) is the partition coefficient, \(D\) is the diffusion coefficient, and \(\Delta x\) is the thickness of the cell membrane.
Note: SI units \(\pu{m s-1}\); frequently used units \(\pu{cm s-1}\), with units \(\pu{cm2 s-1}\) for \(D\), and \(\pu{cm}\) for \(\Delta x\).