Viscoelastic - A true fluid flows when it is subjected to a shear field and motion ceases as soon as the stress is removed. In contrast, an ideal solid subjected to a stress recovers its original state as soon as the stress is removed. Some materials exhibit viscoelastic characteristics having some of the properties of both a solid and a liquid. Two examples of viscoelastic behavior are:

The liquid in a cylindrical vessel is given a swirling motion by means of a stirrer. When the stirring is stopped, the fluid gradually comes to a rest and, if viscoelastic, may then start to rotate in the opposite direction (ie. to unwind).
A viscoelastic fluid, on emerging from a tube or a die, may form a jet which is of larger diameter than the aperture. The phenomenon is referred to as 'die-swell' and results from the sudden removal of a constraining force on the fluid. Viscoelastic fluids are thus capable of exerting normal stresses