In addition to these elementary rules of operation there is also the formation of tensors by differentiation ("erweiterung"):
New tensors, in respect to linear orthogonal transformations, may be formed from tensors according to these rules of operation.
Symmetrical Properties of Tensors. Tensors are called symmetrical or skew-symmetrical in respect to two of their indices,
and
, if both the components which result from interchanging the indices