The term anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or “low oxygen”.
The terms anoxia and hypoxia are used in various contexts:
Hypoxia (environmental), low oxygen conditions.
Hypoxia (medical), when the body or a region of the body is deprived of adequate oxygen supply
Cerebral anoxia, when the brain is completely deprived of oxygen, an extreme form of cerebral hypoxia.