hypoxia

This term describes a physiological state of oxygen deficiency. It is primarily used in medical, aviation, and diving contexts to describe the failure of oxygen to reach the tissues, regardless of whether the cause is a lack of environmental oxygen or a failure in the circulatory system.

As a medical condition, it is an uncountable noun. It refers to a state or a phenomenon rather than a discrete object, meaning it does not have a plural form in standard clinical usage.