Any part of the yam, whole or cut, as long as it has the skin (peel).
root. unlike potatoes which are tubers
No but its mostly a stem. The Yam plant has leaves and roots but the food is the stem of the plant. If you are talking about the food, yes but if you are talking about the plant, no.
The dried root.
No
No. It is a plant.
Yam is a noun.
Yams are a flowering plant. They can be pollinated by insects but camel hair brushes used by humans is more efficient.
Yes
Yam is a noun.
A yam yam is an informal term for a person from the English Midlands, especially one who speaks the Black Country dialect.
Yes
yam capping is the name given to the covering part of the root.