While taking notes in class, I was trying to write the moment of inertia tensor in Einstein notation as Iij instead of a 3x3 matrix, but when we diagonalized the matrix with diagonal elements Ii, I was confused on how to write it. Ii doesn't work because that means that treats it as a vector, instead of a matrix. Iiδij doesn't work for the same reason. Iiδjk doesn't work either because now it's a 3x3x3 tensor. Is there a way to write this out, or am I stuck writing Iij and having to remember that Iii=Ii and Ii≠j=0?