What is a "caryopsis"?

A caryopsis is a type of dry, one-seeded fruit that does not split open at maturity. It is commonly referred to as a grain and is characteristic of grasses, such as wheat, rice, corn, and barley. In a caryopsis, the seed is tightly fused with the fruit wall, making it difficult to separate. This structure provides protection for the seed and aids in dispersal. Caryopses are an important source of nutrition for humans and animals and are a staple food in many cultures around the world.