Cereals are grasses (members of the monocot family Poaceae, also known as Gramineae) cultivated for the edible components of their grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, germ, and bran. Cereal grains are grown in greater quantities and provide more food energy worldwide than any other type of crop.

In their natural form (as in whole grain), they are a rich source of vitamins, minerals, carbohydrates, fats, oils, and protein. However, when refined by the removal of the bran and germ, the remaining endosperm is mostly carbohydrate and lacks the majority of the other nutrients. In some developing nations, grain in the form of rice, wheat, millet, or maize constitutes a majority of daily sustenance. In developed nations, cereal consumption is moderate and varied but still substantial.

The word cereal derives from Ceres, the name of the Roman goddess of harvest and agriculture.

The following table shows annual production of cereals, in 1961,2005, 2006, and 2007 ranked by 2007 production. All but buckwheat and quinoaare true grasses (these two are pseudo-cereals).

Maize, wheat and rice together accounted for 87% of all grain production worldwide, and 43% of all food calories in 2003, while the production of oats and rye have drastically fallen from their 1960s levels. Other grains that are important in some places, but that have little production globally (and are not included in FAO statistics), include:

• Teff, popular in Ethiopia but scarcely known elsewhere. This ancient grain is a staple in Ethiopia. It is high in fiber and protein. Its flour is often used to make injera. It can also be eaten as a warm breakfast cereal similar to farina with a chocolate or nutty flavor. Its flour and whole grain products can usually be found in natural foods stores.
• Wild rice, grown in small amounts in North America
• Amaranth, ancient pseudocereal, formerly a staple crop of the Aztec Empire and now widely grown in Africa
• Kañiwa, close relative of quinoa

Several other species of wheat have also been domesticated, some very early in the history of agriculture:

• Spelt, a close relative of common wheat
• Einkorn, a wheat species with a single grain
• Emmer, one of the first crops domesticated in the Fertile Crescent
• Durum, the only tetraploid species of wheat currently cultivated, used to make semolina
• Kamut, an ancient relative of durum with an unknown history