Dead

Dead refers to the state of an organism that has permanently ceased all vital functions necessary to sustain life. In humans, death is typically defined as either the irreversible cessation of circulatory and respiratory functions or, when those functions cannot be restored, irreversible cessation of all brain activity (brain death). Brain death is legally recognized as death in many jurisdictions, even if some bodily processes such as circulation can be maintained briefly with medical support.

The determination of death involves clinical assessment and, where applicable, legal criteria. Clinically, death may be declared after a period without heartbeat or breathing. In brain death criteria, tests for brainstem reflexes, responsiveness, and the ability to breathe without assistance are used, alongside imaging studies and time-based observations. In some places, circulatory death is declared when circulation and respiration cannot be restored.

Common causes include advanced age, disease (such as cardiovascular conditions, cancers), severe trauma, infections, poisoning, and organ failure. After death, the body undergoes postmortem changes such as pallor, cooling, livor mortis, rigor mortis, and decomposition, and may be preserved or processed for viewing or burial.

Culturally and legally, death marks the end of legal personhood and triggers procedures such as death certification and probate. Societal responses vary, including mourning practices, funerary rites, and organ and tissue donation decisions. Medical advances have extended end-of-life care through palliative and hospice services, and arranged organ transplantation from deceased donors.