Tensile strength is a special case of the solid body, i.e. breaking apart. In the absence of defects such as dislocations or cracks, the ultimate tensile strength of a rod is given by the so-called theoretical (or, more precisely, ideal) strength equal to the order of one tenth of the Young’s modulus. However, under these conditions, real materials fail as a result of either crack propagation (brittle failure), or due to loss of stability of plastic deformation (necking). In any case, strength has the same dimension as stress (MPa, kgf/mm²), which is defined as the ratio of force to the cross-sectional area of the rod.

Tensile strength is an important technical characteristic of a structural material. In many cases, a more important characteristic is the specific strength; that is, the ratio of strength to density. This ratio has the dimension of velocity squared, and serves to evaluate the applicability of the material in structural elements subjected to centrifugal forces. The ratio of strength to specific weight, which has a dimension of length (maximum length of a suspended rod supporting its own weight), is commonly used.