The word grain has a great many meanings, most being descriptive of a small piece or particle. For examples:
- a grain of sand or salt; see grain size for granule
- a grain is a type of simple dry fruit technically called a caryopsis
- in materials science (especially metallurgy), a grain is a single crystal inside solid-state matter, also referred to as crystallite
- a very small unit of weight called a grain
- the fineness of resolution for photographic film (i.e., graininess of a picture)
- wood-grain, and as a description of personality or style from wood-working (i.e. going against the grain)
- also granule, from the diminutive of Latin granum, meaning "grain".