where superscripts label vector components. On the other hand, the plane of the two vectors is represented by the exterior product or wedge product, denoted by . In this context of geometric algebra, this bivector is called a pseudovector, and is the "Hodge dual" of the cross product. The "dual" of e1 is introduced as , and so forth. That is, the dual of e1 is the subspace perpendicular to e1, namely the subspace spanned by e2 and e3. With this understanding,