Which of the following best defines induration?

Induration refers to the process by which tissue becomes hard or firm due to an increase in the density of the interstitial space, often as a result of inflammation or other pathological processes. This can happen due to an accumulation of inflammatory cells, fibrin, or an increase in collagen deposition in the affected area.

In a clinical context, induration can often be a sign of underlying processes such as infection, inflammation, or even malignancy. When palpated, this area has a distinctly firmer feel compared to the surrounding tissues. Recognizing induration is especially important in wound assessment and management, as it can indicate complications like infection or delayed healing.

The other options depict different pathological processes: inflammation, swelling, and necrosis are distinct from the concept of induration, which specifically pertains to the hardening of tissue.