Plasticity

Plasticity is the capacity of a system to undergo a change in form or structure that remains after the triggering influence is removed. The term is used across disciplines to denote irreversible changes in shape, organization, or function in response to stress, experience, or environment. It contrasts with elasticity, where deformations recover when the load is removed.

In materials science, plasticity describes permanent deformation that occurs after a material yields under applied stress. Mechanisms include dislocation motion, twinning, diffusion, or phase changes, depending on the material and temperature. Metals typically exhibit ductile plasticity through dislocation glide; polymers show visco-plastic behavior; ceramics are more brittle. Temperature, strain rate, and prior work influence yield strength and ductility.

In neuroscience, neural plasticity refers to the brain's ability to reorganize its structure and function in response to learning, development, or injury. It encompasses synaptic plasticity, such as long-term potentiation and depression, and structural changes in circuitry. Plastic changes occur throughout life, with heightened plasticity during development and in recovery after damage.

Phenotypic plasticity describes how a single genotype can produce different phenotypes in response to environmental conditions, enabling adaptive responses without genetic change. Plasticity can incur costs and trade-offs and is a focus of study in ecology and evolution. The term is also used in geology to describe the slow, irreversible deformation of rocks under high temperature and pressure.