To regenerate means to grow back or restore something that was lost or damaged. When a starfish loses an arm to a predator, it can regenerate a new one over time. When a lizard's tail breaks off, the lizard regenerates it. Scientists study these abilities closely because most human body parts can't regenerate this way, though our skin regenerates constantly and our liver can regenerate portions of itself if damaged.

The word also applies to renewing or revitalizing something that has declined. A city might work to regenerate a neglected neighborhood by fixing buildings, planting trees, and creating new parks. When forests regenerate after a fire, new growth springs up from the scorched earth. Your body regenerates cells while you sleep, replacing old ones with fresh ones.

In stories and games, characters sometimes have regeneration powers, healing injuries automatically. The word captures this sense of renewal and restoration: taking something worn down or damaged and making it whole and vital again. Whether it's regrowing a limb, rebuilding a community, or restoring energy after a long day, regeneration is nature's and humanity's way of bouncing back.