Cryonics has its own vocabulary, and a surprising amount of confusion about the field is really just confusion about words. This is the short version: the terms you need to read the rest of the Codex without tripping. Where a term has its own article, follow the link for the full treatment.
The state in which biological activity is completely paused without any loss of structural integrity. Here it means holding the body and brain in a stable, non-degrading condition after legal death.
Cryonics
The medical practice of preserving a human at cryogenic temperatures immediately after legal death, with the goal of preventing decay until future medicine can repair and revive them. See how it differs from cryogenics and cryobiology.
Cryogenics
The branch of physics and engineering concerned with producing and controlling very low temperatures, typically below -150°C, and with how materials behave there. Technology, not biology.
Cryobiology
The study of how living systems respond to very low temperatures, and how to protect cells and tissues from the damage that cooling and freezing can cause.
Cryopreservation
The process of preserving biological material at cryogenic temperatures to halt all biological and chemical activity.
A chemical compound that stops ice crystals from forming inside and outside cells during cooling. Cryoprotectants are what make vitrification possible.
The transformation of biological material into a glass-like solid without forming ice crystals. It avoids the structural damage that freezing causes and is the method used in modern cryonics.
Perfusion
Circulating fluids, such as cryoprotectants, through the vascular system to replace blood and protect tissues during cryopreservation.
Stabilization
The first hands-on stage of cryopreservation: rapid cooling, medication, and mechanical circulatory support to slow decay before cryoprotectant perfusion begins.
SST (Standby, Stabilization and Transport)
The operational phase that begins when death is expected or imminent: positioning a team near the patient, beginning medical stabilization the moment legal death is declared, and transporting the patient for cryoprotection and storage.
The point at which a physician declares that vital functions have ceased by current medical standards. It is the moment cryonics procedures are legally allowed to begin.
Clinical death
The temporary cessation of heartbeat and breathing, often reversible if intervention such as CPR happens quickly.
Biological death
The stage at which cellular structures break down and tissue damage becomes irreversible through lack of oxygen and energy.
Information-theoretic death
The point at which the physical structures encoding memory and identity in the brain have been destroyed beyond any possible future recovery. This, not legal death, is the definition cryonics actually cares about.
Cryonics window
The period between legal death and information-theoretic death, during which cryopreservation can still capture the body and brain with high structural integrity.
The temperature, around -130°C, below which molecular motion in vitrified tissue effectively stops, keeping it stable and free of ice.
Liquid nitrogen
The liquefied form of nitrogen gas, which makes up about 78% of the atmosphere. It is colorless, odorless, non-flammable, and boils at -196°C, the temperature used for long-term storage.
Dewar
A vacuum-insulated stainless-steel container that stores cryopreserved patients in liquid nitrogen. It minimizes heat transfer and needs no electricity.
The deprivation of oxygen and nutrients to tissue when blood flow stops, which also lets metabolic waste accumulate and causes progressive cellular damage. Minimizing ischemia after death is critical to preservation quality.
Preservation of the brain or head only, focused on protecting the structures that hold identity and memory.
Whole-body preservation
Preservation of the entire body, including all organs and tissues.
Cryoprotectant toxicity
Cellular damage that can occur when cryoprotectant concentration or exposure time is not carefully controlled. One of the genuine trade-offs of perfusion.
The theoretical future procedure that would restore function and consciousness to a cryopreserved patient once the original cause of death can be repaired. Not currently possible.
Rewarming
The controlled raising of temperature needed to bring vitrified tissue back without cracking or ice formation, one of the harder unsolved steps on the path to revival. Ice that forms during rewarming is called devitrification, and avoiding it takes heating that is both fast and uniform.