The term "vegetable" generally means the edible parts of plants. The definition of the word is traditional rather than scientific, however, and therefore the usage of the word is somewhat arbitrary and subjective, as it is determined by individual cultural customs of food selection and food preparation.

Mushrooms belong to the biological kingdom Fungi, not the plant kingdom, and yet they are also generally considered to be vegetables, at least in the retail industry. Nuts, seeds, grains, herbs, spices and culinary fruits are usually not considered to be vegetables, even though all of them are edible parts of plants. In general, vegetables are those plant parts that are regarded as being suitable to be part of savory or salted dishes, rather than sweet dishes. However there are many exceptions, such as the pumpkin, which can be eaten as a vegetable in a savory dish, but which can also be sweetened and served in a pie as a dessert.

Some vegetables, such as carrots, bell peppers and celery, are eaten either raw or cooked; while others are eaten only when cooked.

The word "vegetable", in its modern usage, is strictly a culinary term, and is not a botanical or scientific term. The word "fruit" on the other hand can be a culinary term, or it can be a botanical term, and these two usages are quite different.

Botanically speaking, fruits are fleshy reproductive organs of plants, the ripened ovaries containing one or many seeds. Thus, many botanical fruits are not edible at all, and some are actually extremely poisonous. A tomato is a botanical fruit but a culinary vegetable.

In a culinary sense however, the word "fruit" is applied only to those botanical fruits or similar plant parts which are both edible and palatable, and which in addition are considered suitable to be a sweet or dessert food, such as strawberries, peaches, plums, etc.

In contrast to this, a number of edible botanical fruits, including the tomato, the eggplant, and the bell pepper, are not considered to be sweet or dessert foods, are not routinely used with sugar, but instead are almost always used as part of a savory dish, and are salted. This is the reason that they are labeled as "vegetables". Thus in a scientific context, a plant part may correctly be termed a "fruit", even though it is used in cooking or food preparation as a vegetable.

The question "The tomato: is it a fruit, or is it 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.

The classification may depend on local culinary traditions as well. For example, in Brazil the avocado is traditionally consumed with sugar as a dessert or in milk shakes, and hence regarded as a fruit; whereas in other countries (including the United States) it is used in salads and dips, and hence considered a vegetable.

  Read More in Wikipedia "Vegetable" »  

See also List of Culinary Vegetables.