Thermometers are used to measure fever in humans or tell you how cold it is outside. Made up of thermo (heat) and meter (measuring device), the meaning of the word thermometer is straightforward. Thermometers measure temperatures in degrees, according to either the Celsius or Fahrenheit system
Digital thermometers are temperature-sensing instruments that are easily portable, have permanent probes, and is equipped with a convenient digital display. The way a digital thermometer works depends upon its type of sensor. Sensor types include resistance temperature detector (RTD), thermocouple and thermistor.
One can use any thermometer, with mouth open, put the end with the red, blue, or silver-coloured tip under your tongue. Close your lips gently around the thermometer. Do not bite the glass thermometer.
Cleaning of the thermometer is also important. It's important to clean the thermometer after each use, but how you clean it depends on what type of thermometer you have. For glass thermometers, wash it with soap and cool water, then rinse and dry. For digital thermometer you can wipe it with a cloth soaked in alcohol or water. Allow it to air dry