The term grain may refer to the following:
- any type of small, coarse, granular particle (e.g. sand, salt, seeds)
- a term for any form of solid propellant charge
- a term for the orientation of weft and warp threads in a woven textile
- a non-metric unit of measurement of mass, approximately equivalent to 64.79891 milligrams, commonly used for measuring bullets, propellants and gunpowder
- a very short part of a musical sample, ranging from about 1-50 milliseconds in length, layered and played back in an unconventional manner in a method of sound synthesis known as granular synthesis
- Crystallite (or grain), a microscopic to small crystal formed during the cooling of a material that make up most inorganic solids
- Food grains, any small, hard fruit or seed of an arable crop, or a crop that bears such fruits or seeds
- Wood grain, a pattern resulting from the longtitudinal arrangement of wood fibers
- Film grain, a random, gritty optical texture sometimes present on images produced using photographic film or paper that may also be used for artistic effect
- Grain size (or particle size), a term referring to the diameter of individual particles or grains of granular materials
- a stream cipher primarily designed for restricted hardware environments that was submitted to the EU ECRYPT network's eSTREAM project in 2004
- an American company that specializes in manufacturing original and custom-designed hollow wooden surfboards
- GRAIN (Genetic Resources Action International, initially International Coalition for Development Action or ICDA), a non-profit, non-government organization for sustainable agriculture and related matters
- Isle of Grain, an isle with a village of the same name in the county of Kent in England
- a quarterly Canadian literary magazine
- an upcoming German/Turkish/French science fiction film