What is Staple Food?

Legal Definition
A staple food, or simply a staple, is a food that is eaten routinely and in such quantities that it constitutes a dominant portion of a standard diet for a given people, supplying a large fraction of energy needs and generally forming a significant proportion of the intake of other nutrients as well. The staple food of a specific society may be eaten as often as every day or every meal, and most people live on a diet based on just a small number of staples.

Staple foods vary from place to place, but typically they are inexpensive or readily-available foods that supply one or more of the three organic macronutrients needed for survival and health: carbohydrates, proteins, and fats. Typical examples of staples include tubers and roots; and grains, legumes, and other seeds. Early agricultural civilizations valued the foods that they established as staples because, in addition to providing necessary nutrition, they generally are suitable for storage over long periods of time without decay. Such nonperishable foods are the only possible staples during seasons of shortage, such as dry seasons or cold temperate winters, against which times harvests have been stored. During seasons of plenty, wider choices of foods may be available.

Most staple plant foods are derived either from cereals such as wheat, barley, rye, maize, or rice; or starchy tubers or root vegetables such as potatoes, yams, taro, arrowroot, or cassava. Other staple foods include pulses (dried legumes), sago (derived from the pith of the sago palm tree), and fruits (such as breadfruit and plantains). Staple foods may also contain (depending on the region): sorghum, olive oil, coconut oil and sugar (e.g. from plantains). Most staples are plant materials, but in some communities fishing is the primary source of nutrition.
-- Wikipedia
Legal Definition
A food that is consumed on a regular basis and provides most of a community's calorie needs. Examples would be rice, corn, and potatoes.