is the (i

is the (i.e. movement) of a solute (e.g. water) across a semi-permeable membrane. Dialysis is the separation (i.e. movement) of molecules themselves.

Osmosis involves water moving from an area of low solute concentration to an area of high solute concentration across a semi-permeable membrane. Dialysis is different to this, and involves the separation of small molecules from large molecules.

Put more simply, dialysis is the movement of molecules in solute (e.g. glucose) and osmosis is the movement of the solvent (water) itself.