Origin: Greek prefix thermo-
Thermometer has 2 different meanings across 1 category:
measuring instrument for measuring temperature
"She quickly took the baby's temperature with a digital thermometer before putting him back down for his nap."
An apparatus used to measure temperature.
"The doctor handed me a thermometer to check my fever before leaving for work."
The word thermometer comes from French, where it combines the prefix thermo- with -meter. It originally referred to an instrument for measuring heat.