The term<unk>  means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms<unk>  and hypoxia are used in various contexts: *<unk>  waters, sea water, fresh water or groundwater that are depleted of dissolved oxygen *<unk>  event, when the Earth's oceans become completely depleted of oxygen below the surface levels * Euxinic,<unk>  conditions in the presence of hydrogen sulfide * Hypoxia (environmental), low oxygen conditions * Hypoxia (medical), when the body or a region of the body is deprived of adequate oxygen supply * Cerebral<unk> , when the brain is completely deprived of oxygen, an extreme form of cerebral hypoxia
Anoxia
Hyperoxia
Hypoxia 
Pseudohypoxia
Cerebral hypoxia
Nitrogen narcosis
Hypoxemia
Hypoventilation