What is the term for a decrease in oxygen content?

The term for a decrease in oxygen content is hypoxia. Hypoxia refers specifically to a condition in which there is insufficient oxygen available to tissues. This can result from various factors, including insufficient oxygen in the environment, respiratory issues, or circulatory problems that prevent adequate oxygen delivery to tissues.

In the context of this question, hypoxia accurately describes the condition focused on the lack of oxygen. It is important to note that while anemia (the first option) involves a reduction in the number of red blood cells or hemoglobin concentration, leading to decreased oxygen-carrying capacity of the blood, it does not directly define a decrease in oxygen content in the tissues themselves. Hypercapnia refers to elevated carbon dioxide levels in the blood, which is not related to oxygen deficiency, while hematocrit measures the proportion of blood volume that is occupied by red blood cells, but again does not define a decrease in oxygen content directly. Hence, hypoxia is the most precise term among the choices presented for a decrease in oxygen content.