  Viscoelastic stress relaxation is a basic characteristic of soft matter
systems such as colloids, gels, and biological networks. Although the Maxwell
model of linear viscoelasticity provides a classical description of stress
relaxation, the Maxwell model is often not sufficient for capturing the complex
relaxation dynamics of soft matter. In this Tutorial, we introduce and dis-cuss
the physics of non-Maxwellian linear stress relaxation as observed in soft
materials, the ascribed origins of this effect in different systems, and
appropriate models that can be used to capture this relaxation behavior. We
provide a basic toolkit that can assist the understanding and modeling of the
mechanical relaxation of soft materials for diverse applications.
