Most traditions have a recognizable cuisine, a specific set of cooking traditions, preferences, and practices, the study of which is known as food science (gastronomy). The study of food is called food science. In English, the substance food is often used metaphorically or figuratively, as in food for thought.

Foods from plants

Food from plant sourcesMany plants or plant parts are eaten as food. There are around two thousand plant species which are cultivated for food, and many have several distinct cultivars. Plant-based foods can be classified as with the nutrients necessary for the plant's initial growth. Because of this, seeds are often packed with energy, and are good sources of food for animals, including humans. In fact, the majority of all foods consumed by human beings are seeds. These include cereals (such as maize, wheat, and rice), legumes (such as beans, peas, and lentils), and nuts. Oilseeds are often pressed to produce rich oils, including sunflower, rape (including canola oil), and sesame.

Fruits are the ripened extensions of plants, including the seeds within. Fruits are made attractive to animals so that animals will eat the fruits and excrete the seeds over long distances. Fruits, therefore, make up a significant part of the diets of most cultures. Some fruits, such as pumpkin and eggplant, are eaten as vegetables. (For more information, see list of fruits.)

Vegetables are other plant matter which is eaten as food. These include root vegetables (such as potatoes and carrots), leaf vegetables (such as spinach and lettuce), stem vegetables (such as bamboo shoots and asparagus), and inflorescence vegetables (such as globe artichokes and broccoli). Many herbs and spices are highly-flavorful vegetables.

Foods from animals

Various raw meatsMeat is eaten, either from muscle systems or from organs. Often other animal products are eaten as well. Mammals produce milk, which in many cultures is drunk or processed into dairy products such as cheese or butter. Birds and other animals lay eggs, which are often eaten. Many cultures eat honey, produced by bees, and some cultures eat animal blood.

Other foods
Some foods do not come from animal or plant sources. These include various edible fungi, including mushrooms. Fungi and ambient bacteria are used in the preparation of fermented and pickled foods such as leavened bread, wine, beer, cheese, pickles, and yogurt. Many cultures eat seaweed, which is a protist, or blue-green algae (cyanobacteria) such as Spirulina. Additionally, salt is often eaten as a flavoring or preservative, and baking soda is used in food preparation. Both of these are inorganic substances, as is water, an important part of human diet.