The term anoxia means a decrease in the level of oxygen to all cells, an extreme form of hypoxia or "low oxygen". Anoxia and hypoxia may occur in various contexts:

• Anoxic sea water
• Anoxic event
• Dead zone (ecology) or hypoxic zones
• Hypoxia (environmental)
• Hypoxia (medical)

See also

• Oxygen saturation, a relative measure of the oxygen dissolved or carried in a medium; a measure of the severity of hypoxic conditions.
• Oxygen toxicity (hyperoxia), the opposite condition of hypoxia, an excess of oxygen in body tissues.