In mathematics, the exterior algebra or Grassmann algebra of a vector space is an associative algebra that contains which has a product, called exterior product or wedge product and denoted with , such that for every vector in The exterior algebra is named after Hermann Grassmann, and the names of the product come from the "wedge" symbol and the fact that the product of two elements of is "outside"
The wedge product of vectors is called a blade of degree or -blade. The wedge product was introduced originally as an algebraic construction used in geometry to study areas, volumes, and their higher-dimensional analogues: the magnitude of a 2-blade is the area of the parallelogram defined by and and, more generally, the magnitude of a -blade is the (hyper)volume of the parallelotope defined by the constituent vectors. Its bilinearity, expected from such a generalization of volume, and its alternating property that implies a skew-symmetric property that and more generally any blade flips sign whenever two of its constituent vectors are exchanged, corresponding to a parallelotope of opposite orientation.