Diffusion (with reference to a cell) means the flow of gaseous molecules from a region of higher concentrarion to a region of lower concentration in/out of the cell.
1. The passive movement of molecules or particles along a concentration gradient, or from regions of higher to regions of lower concentration.
2. The spontaneous net movement of particles down their concentration gradient (i.e. difference in the concentrations of substances or molecules between two areas).
3. (Cell biology): a type of passive transport, therefore, it is a net movement of molecules in and out of the cell across the cell membrane along a concentration gradient.
