Body temperature is defined as the average temperature of the human body. In humans, this average temperature is estimated at around 37°C, although this can vary depending on time of day, typically by 0.5°C in the evening compared to the morning. The center that regulates the body temperature is located in a gland, the pituitary gland, and the exact point of regulation can be changed in the event of damage or disease, hence the outbreak of fever when the body is attacked by infection. This process is distinct, according to purists, from hyperthermia, which defines an increase in body temperature caused by the environment or physical exertion, and hypothermia
, which is a decrease and is essentially due to prolonged exposure to the cold. In both of these cases, the point of regulation is not changed, and the body initiates certain processes designed to bring the temperature back to normal, such as by sweating or shivering.