WITCH: A person, usually female, who practices or professes to practice sorcery. Some believe these powers are derived from the devil. That may be the case in rare situations, but usually this person is a believer in Wicca or the supernatural, and most work good and not evil...
DEMON: The Biblical definition includes evil spirit or fallen angels. This is an entity that does not have its own human form, but rather posses the bodies of others to do its evil works.
As you can see, these two terms are definitely not synonymous with each other and should not be treated as such, Will.
That is all.