A vegetable is an edible plant or part of a plant. However, the word is not scientific, and its meaning is largely based on culinary and cultural tradition. Therefore the application of the word is somewhat arbitrary and subjective. For example, some people consider mushrooms to be vegetables, while others consider them a separate food category. Some vegetables can be consumed raw, and some may (or must) be cooked in various ways.

Fruit or vegetable?

In everyday (non-technical) language, the words “fruit” and “vegetable” are mutually exclusive: plant products that are called fruits are hardly ever classified as vegetables, and vice versa. However, for scientists the word “fruit” also has a precise botanical meaning, which is considerably different from its common meaning. While peaches, plums, and oranges are “fruits” in both senses, many items commonly called “vegetables” — such as eggplants, bell peppers, and tomatoes — are technically fruits, as are also most cereals, as well as some spices like pepper and chiles. On the other hand, many items commonly called “fruits” — including figs, pineapples, and strawberries — are not fruits in the strict botanical sense.
The question of whether the tomato is a fruit or a vegetable found its way into the United States Supreme Court in 1893. The court ruled unanimously in Nix v. Hedden that a tomato is correctly identified as, and thus taxed as, a vegetable, for the purposes of the 1883 Tariff Act on imported produce. The court did acknowledge, however, that, botanically speaking, a tomato is a fruit.
Languages other than English often have categories that can be identified with the common English meanings of “fruit” and “vegetable”, but their precise meaning often depends on local culinary traditions. For example, in Brazil the avocado is traditionally consumed with sugar as a dessert or in milk shakes, and hence it is regarded as a fruit, whereas in other countries (including Mexico and the United States) it is used in salads and dips, and hence considered a vegetable.

Etymology

“Vegetable” comes from the Latin vegetabilis (animated) and from vegetare (enliven), which is derived from vegetus (active), in reference to the process of a plant growing. This in turn derives from the Proto-Indo-European base *weg- or *wog-, which is also the source of the English wake, meaning “become (or stay) alert”.
The word “vegetable” was first recorded in English in the 14th century, but applied to any plant. The word is still used in science with that meaning (e.g., vegetable matter, vegetable kingdom). The meaning of “vegetable” as “plant grown for food” was not established until the 18th century.

Nutrition

Vegetables are eaten in a variety of ways, as part of main meals and as snacks. The nutritional content of vegetables varies considerably, though generally they contain little protein or fat,^[8][9] and varying proportions of vitamins, provitamins, dietary minerals, fiber and carbohydrates. Vegetables contain a great variety of other phytochemicals, some of which have been claimed to have antioxidant, antibacterial, antifungal, antiviral and anticarcinogenic properties.
However, vegetables often also contain toxins and antinutrients such as α-solanine, α-chaconine, enzyme inhibitors (of cholinesterase, protease, amylase, etc.), cyanide and cyanide precursors, oxalic acid, and more. Depending on the concentration, such compounds may reduce the edibility, nutritional value, and health benefits of dietary vegetables. Cooking and/or other processing may be necessary to eliminate or reduce them.

Color pigments

The green color of leafy vegetables is due to the presence of the green pigment chlorophyll. Chlorophyll is affected by pH and changes to olive green in acid conditions, and bright green in alkaline conditions. Some of the acids are released in steam during cooking, particularly if cooked without a cover.
The yellow/orange colors of fruits and vegetables are due to the presence of carotenoids, which are also affected by normal cooking processes or changes in pH.
The red/blue coloring of some fruits and vegetables (e.g. blackberries and red cabbage) are due to anthocyanins, which are sensitive to changes in pH. When pH is neutral, the pigments are purple, when acidic, red, and when alkaline, blue. These pigments are very water soluble.

Safety

For food safety, the CDC recommends proper fruit handling and preparation to reduce the risk of food contamination and foodborne illness. Fresh fruits and vegetables should be carefully selected. At the store, they should not be damaged or bruised and pre-cut pieces should be refrigerated or surrounded by ice. All fruits and vegetables should be rinsed before eating. This recommendation also applies to produce with rinds or skins that are not eaten. It should be done just before preparing or eating to avoid premature spoilage. Fruits and vegetables should be kept separate from raw foods like meat, poultry, and seafood, as well as any cooking utensils or surfaces that may have come into contact with them (e.g. cutting boards). Fruits and vegetables, if they are not going to be cooked, should be thrown away if they have touched raw meat, poultry, seafood or eggs. All cut, peeled, or cooked fruits and vegetables should be refrigerated within 2 hours. After a certain time, harmful bacteria may grow on them and increase the risk of foodborne illness.

Storage

Proper Post Harvest Storage aimed at extending and ensuring shelf life is best affected by efficient cold chain application. All vegetables benefit from proper post harvest care.
Many root and non-root vegetables that grow underground can be stored through winter in a root cellar or other similarly cool, dark and dry place to prevent mold, greening and sprouting. Care should be taken in understanding the properties and vulnerabilities of the particular roots to be stored. These vegetables can last through to early spring and be nearly as nutritious as when fresh.
During storage, leafy vegetables lose moisture, and the vitamin C in them degrades rapidly. They should be stored for as short a time as possible in a cool place, in a container or plastic bag.