In botany, a caryopsis 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 caryopsis the pericarp is fused with the thin seed coat. The caryopsis is loosely called a grain and is the fruit typical of the Family Poaceae. Examples of plants that produce a caryopsis fruit are wheat, rice, and corn. In these fruits, the "hulls" to be separated from many grains before processing are actually flower bracts.

The term grain is also used in a more general sense as synonymous with cereal (as in cereal grains). Considering that the fruit wall and the seed are intimately fused into a single unit, and the caryopsis or 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 plant structures.