toughen

Toughen is a verb meaning to make something tougher or to become tougher. It can refer to increasing the physical resilience of an object or to harden or strengthen something, such as materials, policies, or a person.

Etymology: toughen derives from the adjective tough plus the English suffix -en. The form appears in Late Middle English and has since developed to cover both the active process of making something tougher and the stative sense of becoming more resilient.

In materials science, toughening describes processes that raise a material's toughness, the ability to absorb energy before fracturing. Methods include heat treatment, alloying, and microstructural modifications, as well as the addition of composites or rubber modifiers in polymers. Examples include steel tempered to improve toughness and tempered glass, which is strengthened by surface compressive stresses.

In everyday use, "toughen up" refers to mentally or emotionally becoming more resilient or to strengthen a system or policy through experience, training, or enforcement. The expression is informal and can be heard in education, sports, or law enforcement, with debate about whether it promotes resilience or hardship.

Related terms include toughness, tough, toughening, and toughened. The concept is connected to hardening and fortification, though toughness emphasizes resistance to fracture and energy absorption rather than merely hardness.