Thermoregulation

2.77 Understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis.

Homeo is the idea of something being the 'same'.  
Stasis refers to the idea of a fixed point or a set of conditions.

Homeostasis is the idea that the conditions are kept the same or constant.

Homeothermic is the idea of maintaining the same temperature.

Some organisms (e.g. mammals) which when the environmental temperature increases or decreases, their body temperature stays constant. These are homeothermic organisms.

The carry a process called thermoregulation, an example of homeostasis.

Mammals need to maintain a constant body temperature because of rates of reactions and to prevent denaturing (enzymes).

The optimum temperature for the enzymes, tends to be the temperature that the mammals maintain their body at.