Someone once asked what the difference between a bun and a chignon. Well, not much. If you look at the true definition, you will see that they are very similar.
chi·gnonnoun \ˈshēn-ˌyän also -ˌyȯn\
Definition of CHIGNON
: a knot of hair that is worn at the back of the head and especially at the nape of the neck
: a sweet or plain small bread; especially : a round roll
: a knot of hair shaped like a bun
plural : buttocks
It really is all relative. I would consider a chignon to be on the lower part (nape) of the head with a smoother shape. The bun can be anywhere on the head with a twisted or braid pattern. Like how I wore the back of my hair on day 4, I would consider that to by a bun. Really, I don't think the world would end if you called a bun a chignon and a chignon a bun. As long as it's pretty in the end. Right?
Have a happy hair day!