2.81 understand that homeostasis is the maintenance of a constant internal environment, and that body water content and body temperature are both examples of homeostasis

Homeostasis: regulations of conditions inside body
Homeostasis includes osmoregulation and thermoregulation.

Osmoregulation: Control of water levels in body
Thermoregulation: Keeping the body at optimum body temperature (37°C)
e.g. When hot you sweat so sweat is evaporated to cool you down. When cold your hairs stick out for an extra layer of insulation.