Because the first term, which is Ω Ω × × ( Ω Ω × × X A B ) , is of the same form as the normal centrifugal force expression: Ω Ω × × ( Ω Ω × × x B ) , it is a natural extension of standard terminology (although there is no standard terminology for this case) to call this term a "centrifugal force". Whatever terminology is adopted, the observers in frame B must introduce a fictitious force, this time due to the acceleration from the orbital motion of their entire coordinate frame, that is radially outward away from the centre of rotation of the origin of their coordinate system: