English: In two dimensions, 4 independent parameters are required to describe a tensor. The straight arrows represent eigenvectors and eigenvalues of the symmetric component of the tensor: The first arrow is specified using two variables. These parameters can be (1) the magnitude of the eigen value, and (2) the direction of the eigenvector. The second eigenvector is constrained in direction (to be perpendicular to the first), while that vectors magnitude (eigenvalue) is (3) the third parameter. The final parameter (4) is the magnitude of a vector that is perpendicular to the plane. This magnitude is represented by the size of the circular direction arrow. This fourth parameter is not required if the tensor is symmetric.