Viscoelasticity is the study of materials that exhibit both viscous (fluid-like) and elastic (solid-like) behavior when subjected to mechanical stress. These materials can deform under stress and return to their original shape when the stress is removed, but they do so with a time-dependent response. This means that their behavior is influenced not only by the applied stress, but also by the rate at which the stress is applied. Viscoelastic materials are commonly found in nature, such as in biological tissues, as well as in a wide range of industrial applications, including polymers, gels, and food products. Understanding viscoelasticity is important in fields such as materials science, biomechanics, and rheology, as it affects the mechanical properties and performance of materials in various applications.