Clinical thermometer is used for measuring the temperature of human. It is marked in degree Centigrade or degree Fahrenheit. The temperature of a healthy human body is approximately 98.6°F. To measure the temperature a person has to hold the tip of the thermometer either under the armpit or in the mouth under his tongue for a minute. Then we observe the number against the point at which the mercury column stop rising further indicates the body temperature of the person. Notes: 1. A human body suffering from fever has body temperature above 98.6°F. 2. A human body does not have temperature below 94°F or 34.4°C and above 108°F or 42.2°C. 3. A grown up person never has temperature above 105°F or 40.5°C and a child never has a temperature above 107°F or 41.6°C. 4. During the day time, the normal body temperature rises by 1.8°F or 1°C. 5. The temperature is lowest in the morning and highest in the afternoon.