$Q=qT$

NOTE 1 A tensor quantity often describes a linear transformation of a vector quantity U into a vector quantity V:

$V_i={\displaystyle \sum _j{Q}_{ij}}{U}_j$

NOTE 2 The expression of a tensor quantity in terms of its components is similar to the expression of vector quantities (see Note 1 to 102-03-22). Examples of tensor quantities are the permittivity and the permeability in anisotropic media, see IEC 60050-121.

NOTE 3 Operations defined for tensors apply to tensor quantities.