Grain
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
- in materials science (especially metallurgy), it 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".
In BOTANY, a grain is a type of simple dry fruit, one that is moncarpelate (formed from a single carpel) and indehiscent (not opening at maturity) and resembles an achene, except that in a grain the pericarp is fused with the thin seed coat. Examples of grains are wheat, rice, and corn — the fruit of these and other grasses (Family Poaceae) are grains. The "hulls" to be separated from many grains before processing are flower bracts.
The term grain is also used in a more general sense as synonymous with cereal or cereal grains. Considering that the fruit wall and the seed are intimately fused into a single unit, and the grain is a dry fruit, it is not surprising that in general usage little concern is given to technically separating the terms "fruit" and "seed" in these fruits.