Page "Rheology" Paragraph 13

# Even if both strain and rate of strain are infinitesimal, a system may exhibit both liquid-like and solid-like characteristics.

A good example of this is when a body which is not quite an elastic solid ( i. e. an inelastic solid ) does not maintain a constant deformation under constant stress, but rather continues to deform with time – or " creeps " under the same stress at constant temperature.

When such a body is constrained at constant deformation, the stress required to hold it at that stretch level gradually diminishes — or " relaxes " with time.