In an oscillation shear experiment, the material is subjected to either a sinusoidal strain or stress and the corresponding response is measured. The ratio of the output and input signals is referred to as the transfer function or material function (Figure 1). When a sinusoidal deformation or deformation rate is applied, the material’s response is the stress. The resulting material function is either the modulus or the viscosity; if a stress is applied and the strain measured, the material function is the compliance.