physiological

This word focuses on the mechanical and chemical operations of a living body. It describes the "hardware" of existence—how organs, cells, and systems actually function to keep an organism alive.

In practical usage, it is most frequently used as a counterpoint to "psychological." While psychological refers to the mind, emotions, and mental states, physiological refers to the physical reality of the body (e.g., a physiological response like sweating vs. a psychological response like fear).

It carries a clinical, scientific, and objective tone. It is rarely used in casual conversation unless discussing health, athletics, or science, as it implies a level of biological precision.