By referring collectively to e 1, e 2, e 3 as the e basis and to n 1, n 2, n 3 as the n basis, the matrix containing all the c jk is known as the " transformation matrix from e to n ", or the " rotation matrix from e to n " (because it can be imagined as the "rotation" of a vector from one basis to another), or the " direction cosine matrix from e to n " (because it contains direction cosines). The properties of a rotation matrix are such that its inverse is equal to its transpose. This means that the "rotation matrix from e to n " is the transpose of "rotation matrix from n to e ".