Yield or Yield is the irrecoverable deformation of a specimen "Template (mechanical)") or material that presents plasticity "Plasticity (solid mechanics)"), from which only the part of its deformation corresponding to the elastic deformation will be recovered, leaving an irreversible deformation. This phenomenon is located just above the elastic limit, and a very rapid elongation occurs without changing the applied tension. Through a tensile test, this characteristic deformation is measured, which not all materials experience.[1]​.

The creep phenomenon occurs when impurities or alloying elements block the dislocations "Dislocation (crystalline defect)") of the crystalline network, preventing its sliding, a process by which the material is plastically deformed.

Once the yield limit is reached, the dislocations are released, producing a sudden deformation. The deformation in this case is also distributed uniformly throughout the specimen, but concentrating in the areas in which the dislocations have been released (Lüders bands). Not all materials present this phenomenon, in which case the transition between elastic and plastic deformation of the material is not clearly appreciated.

It can be seen graphically in the stress-strain curve obtained after the tensile test: the creep period is 2.

The yield limit is the point where the phenomenon known as creep begins, which consists of a very rapid elongation without changing the tension applied in a tensile test. Up to the yield point, the material behaves elastically, following Hooke's law, and therefore Young's modulus can be defined. Not all elastic materials have a clear yield point, although it is generally well defined for most metals.

Also called apparent elastic limit, it indicates the stress supported by a tensile test specimen at the time of the yield or creep phenomenon. This phenomenon takes place in the transition zone between elastic and plastic deformations and is characterized by a rapid increase in deformation without an appreciable increase in the applied load.

In general three-dimensional plasticity "Plasticity (mechanics of solids)"), the yield point is not a specific point on a curve, but can be represented by a surface closed and enclosing a finite volume in the space of principal stresses, called yield surface. Furthermore, in some materials that present hardening, the yield surface is not fixed but depends on the previous stress history. In any case the yield surface always moves outwards from itself.