In the
grass family, a grain (narrowly defined) is a caryopsis, a fruit with its wall fused on to the single seed inside, belonging to a cereal such as wheat, maize, or rice. More broadly, in
agronomy and commerce, seeds or fruits from other plant families are called grains if they resemble cereal caryopses. For example,
amaranth is sold as "
grain amaranth", and amaranth products may be described as "whole grains". The
pre-Columbian civilizations of the Andes had grain-based food systems, but at higher elevations none of the grains belonged the cereal family. All three grains native to the Andes (
kaniwa,
kiwicha, and
quinoa) are broad-leaved plants rather than grasses. == Cereal grains ==