The answer is
a process by which organisms keep internal conditions relatively constant despite changes in external conditions
The homeostasis is an organism's ability to maintain a stable internal environment. It is a mechanism that controls internal conditions of an organism so that internal conditions remain stable without regard to the external conditions. So, it regulates body temperature, water level, sugar level, etc. For example, if body temperature is increased, the body detects the change and activate mechanisms that decrease body temperature.
