  In the mesoscopic theory a distribution of different crack sizes and crack
orientations is introduced. A scalar damage parameter, a second order damage
tensor and a vectorial damage parameter are defined in terms of this
distribution function. As an example of a constitutive quantity the free energy
density is given as a function of the damage tensor. This equation is reduced
in the uniaxial case to a function of the damage vector and in case of a
special geometry to a function of the scalar damage parameter.
