This article is about food that starts with a for all organisms. For food for humans, see Human food. Food is any substance consumed by an organism for nutritional support.

Omnivorous humans are highly adaptable and have adapted to obtain food in many different ecosystems. Food is any substance consumed to provide nutritional support and energy to an organism. It can be raw, processed or formulated and is consumed orally by animals for growth, health or pleasure. Human food can be classified in various ways, either by related content or by how the food is processed.

The number and composition of food groups can vary. Most systems include four basic groups that describe their origin and relative nutritional function: Vegetables and Fruit, Cereals and Bread, Dairy, and Meat. In a given ecosystem, food forms a web of interlocking chains with primary producers at the bottom and apex predators at the top. Humans are omnivores finding sustenance in vegetables, fruits, cooked meat, milk, eggs, mushrooms and seaweed. Cereal grain is a staple food that provides more food energy worldwide than any other type of crop.