immortal

Immortal is an adjective describing beings or things that cannot die of natural causes. In common usage it refers to beings believed to possess infinite life, or to objects that do not degrade over time. The term derives from Latin immortalem, from in- "not" and mortalem "mortal" (hence "not mortal"). In everyday language it often connotes supernatural or transcendent longevity, though in scientific contexts it can describe biological immortality — the absence of aging as a primary cause of death.

Biological immortality is a theoretical or observed condition in which the organism does not experience increasing mortality with age. Some species show negligible senescence, including certain jellyfish, hydra, and some planarians. In such cases individuals can still die from injury, disease, or environmental factors. Most organisms, including humans, experience aging, progressive functional decline, and higher risk of death with time. Researchers study mechanisms such as cellular senescence, telomere dynamics, and regenerative capabilities to understand aging and to develop therapies aimed at extending healthy lifespan rather than true immortality.

In religion and philosophy, immortality often refers to the beyond-physical persistence of the soul or consciousness, or to eternal life granted by divine power. Concepts of immortality vary widely across cultures and faiths, ranging from personal eternal existence to reincarnation or spiritual continuation after death.

In fiction, immortality is a common motif used to explore themes of power, responsibility, memory, and consequence. Characters may be physically unaging or exist across centuries, sometimes at a cost or with trade-offs such as loss of humanity or vulnerability to other forms of harm.