The onion is completely edible. The skin, though papery and edible is usually removed as is the small root at the bottom of the bulb. these two parts are less palatable and usually discarded. The bulb and leaves (green onion) are used in a large variety of ways.
The entire onion plant is edible.
no it is not All parts of the plant are edible and can be used as you would spring onions.
an edible circle is an onion ring
aerial stem
onion
An onion, strictly speaking, is a 'bulb' and is a stem.
Allium cepa, the botanical name for the Onion
There is a thin layer of dry, papery skin on an onion bulb which has to be peeled off, and is not edible; every other part of the onion is edible, including the leaves if the bulb is allowed to sprout. Raw onion has a rather strong flavor, which has to be used in moderation - just a bit of chopped raw onion is nice on a hamburger. Fried onion develops a much milder, savory flavor. Chopped onion leaves (green onion) go well in soup.
I think the word you're looking for is onion, as in the edible plant.
fibrous root
It is the bulb, which is also the edible part.
Beans are contained inside the bean pod which is also edible. These pods grow on climbing vines.