Grains are small, hard, dry seeds (with or without hull or fruit layers attached) harvested for human food or animal feed [1] Agronomists also call the plants producing such seeds grains or grain crops.
Harvested, dry grain has advantages over other staple foods such as the starchy fruits (e.g., plantain, breadfruit) and roots/tubers (e.g., sweet potato, cassava, yam) in being easy to store, handle and transport. In particular, these qualities have allowed mechanical harvesting, shipping of grain by rail or surface, long-term storage in grain silos, large-scale milling or pressing and industrial agriculture in general. Thus, major commodity exchanges deal with soybean, rice, wheat, maize, canola and other grains but not in vegetables, tubers or many other crops.[2]
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In Botany, the term is synonymous with caryopses, the fruits of members of the grass family, but in agronomy and commerce, seeds or fruits from other families are also called grains if they resemble caryopses. For example, amaranth is sold as "grain amaranth" and amaranth products may be described as "whole grain."[3] The pre-Hispanic civilizations of the Andes had grain based food systems, but in the higher elevations, none of the grains were cereals.[4]
Cereal crops are all members of the grass family[5] Cereal grains contain much starch, a carbohydrate that provides dietary energy.
Starchy grains from broadleaf (dicot)plant families
Members of the (pea family). Pulses have higher protein than most other plant foods. They may also contain starch or oil. Most widely grown include:
Grains grown primarily for the extraction of their edible oil. Vegetable oils provide dietary energy and some essential fatty acids. They can be used as fuel or lubricants.
Grains—being small, hard and dry—can be stored, measured, and transported more readily than other kinds of food crops, such as fresh fruits, roots and tubers. The advent of grain agriculture allowed excess food to be produced and stored easily for the first time which could have led to both the creation of the first permanent settlements and the division of society into classes.[6]