In materials science, liquefaction is a process that generates a liquid from a solid or a gas or that generates a non-liquid phase which behaves in accordance with fluid dynamics. It occurs both naturally and artificially. As an example of the latter, a "major commercial application of liquefaction is the liquefaction of air to allow separation of the constituents, such as oxygen, nitrogen, and the noble gases." Another is the conversion of solid coal into a liquid form usable as a substitute for liquid fuels.

पदार्थ विज्ञान के सन्दर्भ में द्रवण (Liquefaction) उन सभी प्रक्रियाओं को कहते हैं जो ठोस से या द्रव से आरम्भ होकर गैस बनाते हैं।