The unit vector along tangent, principal normal, and binormal are denoted by t^,n^,b^ and form an orthogonal right handed triad so we can say that t^.n^ =0, n^.b^= 0, b^.t^ =0 & t^ ×n^ =b^ ,b^ ×t^ =n^, n^ ×b^ =t^. the set of unit vectors t^,n^,b^ which vary from point to point along a curve form a moving trihedral and they are independent of parameterization and determine the local property of the curve at that point. Hence t^,n^,b^ are called Fundamental Unit Vector. The three planes osculating plane, normal plane & rectifying plane are associated with each point of curve and are known as Fundamental Plane.
