What does thermometer mean?
A thermometer is an instrument that measures temperature, indicating the degree of heat or cold in the surrounding air, a liquid, or a person's body. Digital thermometers, mercury thermometers, and other designs use different technologies, but all serve the same basic purpose: turning a physical condition into a readable measurement. The word is common in medicine, weather observation, laboratories, cooking, and everyday household discussion. A doctor uses a thermometer to check for fever, while a weather observer uses one to record changing atmospheric conditions. In figurative language, a person or place may be called a thermometer of public opinion when its reactions reveal the mood of a wider group. The term comes from Greek roots meaning “heat” and “measure.” Its development grew out of early scientific instruments, including Galileo Galilei's thermoscope. Today, a thermometer is valued not only for its practical readings but also as a simple symbol of careful measurement and objective observation.
nounA thermometer is an instrument used to measure temperature, especially the temperature of the air, a liquid, or the body. By extension, it can refer figuratively to a person or thing whose reactions indicate how strongly a particular feeling or opinion is held.
- An instrument for measuring temperature.
- A person, group, or thing regarded as indicating the strength of public feeling or opinion.
"The doctor placed a digital thermometer under the patient's tongue."
"The temperature fell sharply after midnight, according to the outdoor thermometer."
"The town became a thermometer of public opinion after the announcement."
The regular plural adds -s to the noun.
"The clinic keeps several thermometers in separate protective cases."
Galileo's thermoscope helped turn the ancient idea of measuring heat into one of the most familiar instruments in everyday life.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does thermometer come from?
Thermometer combines the Greek noun thermē, meaning “heat,” with metron, meaning “measure.” The word belongs to the early modern period of scientific vocabulary, developing from earlier heat-measuring instruments such as Galileo Galilei's thermoscope. Its relatives include thermal, therm, temperature, and thermoscope, all reflecting the same Greek association with heat.
Related word forms
How thermometer is actually used
The word is neutral and technical in ordinary use. Its figurative sense is less common and often suggests that someone is unusually sensitive to changing attitudes or emotions.
Easily confused with thermometer
A thermometer measures temperature, whereas a barometer measures atmospheric pressure and is commonly used to help forecast the weather.