Mass Transfer is the phrase commonly used in engineering for physical processes which involve molecular and convective mixing of atoms and molecules in systems comprised of gases and liquids.

Some common examples of mass transfer are evaporation of water from a pond to the atmosphere; the diffusion of chemical impurities in lakes, rivers, and oceans from natural or artificial point sources; and the pleasant smells of perfume or aftershave encountered in a social setting.


In astronomy, mass transfer is the process by which matter gravitationally bound to a body, usually a star, fills its Roche lobe and becomes gravitationally bound to a second body, usually a compact object (white dwarf, neutron star or black hole), and is eventually accreted onto it. It is a common phenomenon in binary systems, and may play an important role in some types of supernovae, and pulsars.