The entire onion plant is edible.
An onion, strictly speaking, is a 'bulb' and is a stem.
It is the bulb, which is also the edible part.
an edible circle is an onion ring
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.
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.
onion
Some consider it to be a week but it is edible! Onion grass is just like chives, you can eat the bulb and grass part! Just make sure it is the onion grass with the hollow grass and white bulbs and you will never have to buy chives from the supermarket again!
Allium cepa, the botanical name for the Onion
the part of the flower that is edible
I think the word you're looking for is onion, as in the edible plant.
fibrous root