deformatsioon, mida saab väljendada mingis deformatsioonifaasis oleva keha mõõtme ja algmõõtme jagatise naturaallogaritmina: e = ln L/Lo (vt deformatsioon), 1. the ratio of the change in dimensions, resulting from a given load, increment to magnitude of dimension immediately prior to applying the load increment; 2. in a body subjected to axial force, the natural logarithm of the ratio of the gauge length at moment observation to the original gauge length (see: deformation)