Abnormally low partial pressure of oxygen in arterial blood.
Hypoxemia is different from hypoxia in a way that the latter refers to a condition where oxygen supply to tissues is abnormally low. It is also possible that the oxygen content is low while the partial pressures in arterial blood are high, such as caused by anemia. Nonetheless, hypoxia caused by hypoxemia is referred to as hypoxemic hypoxia.
Related forms: hypoxemic (adjective).