Most engineered components are designed to act elastically, meaning that when loads are released, the component will return to its original, undeformed configuration. For proper design, therefore, it is important to define the stress at which the material will no longer behave elastically.

With most materials, there is a gradual transition from elastic to plastic behavior, and the point at which plastic deformation begins is difficult to define with precision. One measure that has been used to establish this threshold is termed the elastic limit.