What is the definition of homeostasis?

Answer 1

The maintenance of a constant internal environment despite changes in the external environment.
The word itself means "unchanging." It describes the body's ability maintain relatively stable internal conditions even though the outside world is changing.
It's homeostasis, not homoeostasis, and it means to keep an environment under constant conditions, or to keep it stable.

Ex: Human homeostasis is the internal body stays the same temperature: 98.6 degrees F, or about 37 degrees C. If the temperature rises or falls the human may be ill, and if the temperature is too far off the normal, then the human dies. Things like fevers and hypothermia can change body temperature, fighting homeostasis.

Answer 2

Homeostasis is the ability of an organism to maintain internal stability and balance in response to external changes. It involves the regulation of various physiological processes to keep conditions within a narrow range that is conducive to life.