"A vegetable is an edible plant or part of a plant, but usually excludes seeds and most sweet fruit. This typically means the leaf, stem, or root of a plant.
The non-biological definition of a vegetable is largely based on culinary and cultural tradition. Therefore, the application of the word is somewhat arbitrary, based on cultural and/or personal views. For example, some people consider mushrooms to be vegetables even though they are not biologically plants, while others consider them a separate food category; Some cultures group potatoes with cereal products such as noodles or rice, while most English speakers would consider them vegetables.
Some vegetables can be consumed raw, some may be eaten cooked, and some must be cooked in order to be edible. Vegetables are most often cooked in savory or salty dishes. However, a few vegetables can be used in desserts and other sweet dishes, such as pumpkin pie and carrot cake. A number of processed food items available on the market contain vegetable ingredients and can be referred to as "vegetable derived" products. These products may or may not maintain the nutritional integrity of the vegetable used to produce them..."
http://en.wikipedia.org/wiki/Vegetable
