Viscoelastic materials have properties of both viscosity and elasticity. This means they can deform when a force is applied, like a liquid, but can also return to their original shape when the force is removed, like a solid. Common examples include rubber and polymer materials, which are used in various applications due to their ability to absorb energy and reduce shock. The behavior of viscoelastic materials is time-dependent, meaning their response to stress can change over time. When stretched or compressed, they may exhibit a gradual deformation, which is characteristic of viscosity. This unique combination of properties makes viscoelastic materials important in fields like engineering and medicine.