Initially the word “vegetable” was used in science to distinct plants from other forms of life. They describe the vegetation. However, its current use is mainly applied in culinary. Veggies are the parts of various plants consumed by people raw or cooked. This food group does not include fruits or berries. However, it may include nuts or seeds and various greens. So, basically, vegetables are the plant foods (as opposed to animal sources of food).
At first the word “vegetable” was used only in science to distinct vegetable life (plants) from animals, insects or mushrooms. Presently, it is used on culinary to distinguish plant food from animal one. However, it does not include all the plant food, excluding fruit and berries. Plus “vegetable” means the eatable part of the plant vs. uneatable one: the roots or greens, seeds or fruit you can eat. Vs. roots, greens or branches you cannot consume.