thermometer /thermom′ətər/ [Gk, thermē + metron, measure] , an instrument used to measure temperature. The first thermometers consisted of a sealed glass tube, marked in degrees Celsius or Fahrenheit, filled with either mercury or alcohol; the liquid in the tube would rise or fall as it expanded or contracted, based on changes in temperature. There are now many types of thermometers. Kinds include air thermometer, clinical thermometer, digital thermometer, electronic thermometer, mercury thermometer, rectal thermometer, surface thermometer, tympanic membrane thermometer, wet-and-dry-bulb thermometer.
