Physiological means relating to how a living body normally works and functions. When doctors talk about physiological processes, they mean things like how your heart pumps blood, how your lungs take in oxygen, or how your stomach digests food.

The word helps distinguish physical body functions from mental or emotional ones. A physiological response to fear might include a faster heartbeat and sweaty palms: your body's automatic reaction. Compare this to a psychological response, which involves your thoughts and feelings. When you get nervous before a presentation, the butterflies in your stomach are physiological, while your worried thoughts are psychological.

Scientists study physiological changes to understand how bodies work under different conditions. They might measure a runner's physiological responses during a race: breathing rate, heart rate, body temperature. Athletes train to improve their physiological performance, making their bodies more efficient at using oxygen and energy.

When something is physiological, it's about the machinery of life itself: the pumping, breathing, digesting, and growing that keeps organisms alive and healthy.