Question

why is the thermometer kept under the tongue?

Answer 1

because that's a location where outside temp doesnt mix with the body temp

Answer 2

Thermometer is kept under tongue so that the reading which it gives is true , i.e. true reading of the inner body heat. The intense heat of our body is present under our tongue and so it is used under tongue so that we can measure our whole body temperature . The underside of the tongue has the most bloodflow and is more accurate than any part of the mouth. If thermometer will be in contact with air at the same time , then it will cool down and will result in giving incorrect reading. So it is kept under tongue.