Normal human body temperature, also known as normothermia or euthermia, depends upon the place in the body at which the measurement is made, and the time of day and level of activity of the person. Despite the popular belief, there is no single number that represents a normal or healthy temperature for all people under all circumstances using any place of measurement. Different parts of the body have different temperatures. Rectal and vaginal measurements, or measurements taken directly inside the body cavity, are typically slightly higher than oral measurements, and oral measurements are somewhat higher than skin temperature. The commonly accepted average core body temperature (taken internally) is 37.0 °C (98.6 °F). However, this is actually a 19th Century approximation by German Physician Dr. Carl Wunderlich. The Celsius value is set on an even degree, with the Fahrenheit merely being an overly-precise approximation.[1] The typical oral (under the tongue) measurement, which the cited Harvard study agrees with exactly as the true average human body temperature, is slightly cooler, at 36.8° ± 0.4°C (98.2° ± 0.7°F), and temperatures taken in other places (such as under the arm or in the ear) produce different typical numbers.[2] Although some people think of these numbers as representing the normal temperature, a wide range of temperatures has been found in healthy people.[3]

Variations in body temperature are part of the circadian rhythm (see at 4:30 and