Vegetable is a culinary term which has no botanical meaning. Although the concept is generally understood, the popular definition of "vegetable" is imprecise and incomplete. At best a vegetable can be defined as "a plant, usually herbaceous, of which any part is eaten in savoury dishes". The edible parts may be leaves, roots, tubers, bulbs, stems, pods, flowers or seeds. Some fruits are also treated as vegetables.
Most vegetables are cultivated, having been developed from wild predecessors. There are a vast number of species, within which are numerous cultivars, each with different properties and differing nutritional profiles, but most are rich in essential nutrients and fibre, while low in fat. Accordingly, vegetables are generally considered a vital part of a well-balanced diet
With some notable exceptions, vegetables are best eaten frehly picked. Because they continue to live when harvested from the plant, vegetables use their own stored sugar to carry on, and thus their sweetness, flavour and, sometimes, their texture, deteriorates. As they age, water loss causes them to wilt and microbes may spoil them. Locally grown produce is more likely to be freshly picked, while produce in season is likely to be local.
"Fungi" in the vegetable sense denotes mushrooms and truffles. The part eaten is the fruiting body. Primitive organisms, fungi are in a class of their own; as they do not contain chlorophyll they do not photosynthesize sugars so are saprophytic, living symbiotically on the decaying remains of other organisms. They differ from higher plants in composition, their cell walls being made not from cellulose but less-digestible chitin.
Not nutritionally significant, fungi are eaten for their rich, almost meaty, flavour and texture and, in some cases, their unique aroma. They intensify flavours, like a natural version of monosodium glutamate, due to their high content of glutamic acid. Some fungi are cultivated, but most must be gathered wild. This, and their superior flavour, makes wild fungi highly prized. As some are toxic, wild fungi should be positively identified before consumption.