thermometer

American  

[ther-mom-i-ter] / θərˈmɒm ɪ tər /

noun

thermometers plural

1. an instrument for measuring temperature, often a sealed glass tube that contains a column of liquid, as mercury, that expands and contracts, or rises and falls, with temperature changes, the temperature being read where the top of the column coincides with a calibrated scale marked on the tube or its frame.

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thermometer British  

/ θəˈmɒmɪtə /

noun

1. an instrument used to measure temperature, esp one in which a thin column of liquid, such as mercury, expands and contracts within a graduated sealed tube See also clinical thermometer gas thermometer resistance thermometer thermocouple pyrometer

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thermometer Scientific  

/ thər-mŏm′ĭ-tər /

1. An instrument used to measure temperature. There are many types of thermometers; the most common consist of a closed, graduated glass tube in which a liquid expands or contracts as the temperature increases or decreases. Other types of thermometers work by detecting changes in the volume or pressure of an enclosed gas or by registering thermoelectric changes in a conductor (such as a thermistor or thermocouple).

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Other Word Forms

Derived Forms

• thermometric
  adjective
• thermometrical
  adjective
• thermometrically
  adverb

Inflected Forms

Nouns

• thermometers
  plural

Etymology

Origin of thermometer

First recorded in 1615–25; thermo- + -meter

Explanation

A thermometer is a tool that measures temperature — how hot or cold something is. Thermometers are used to see if you have a fever or tell you how cold it is outside. Made up of thermo (heat) and meter (measuring device), the meaning of the word thermometer is pretty straightforward. Thermometers measure temperatures in degrees, according to either the Celsius or Fahrenheit system. Meteorologists use thermometers to find out how hot it is or if it's below freezing. Doctors use thermometers to check your body temperature — a very high or low body temperature means you're sick.

Example Sentences

Drizzle could dampen Southern California on Monday and Tuesday before a heat wave arrives just in time for Mother’s Day weekend — possibly pushing the thermometer to 90 degrees in downtown L.A. on Sunday.

From Los Angeles Times • May 4, 2026

Basically, he wrote a hit piece on the thermometer instead of asking why he had a fever.

From Slate • Apr. 17, 2026

In mid-January, graphic designer Oleksandra Skachkova posted a TikTok video of herself drinking her morning coffee beside a thermometer reading 53 degrees Fahrenheit.

From The Wall Street Journal • Mar. 10, 2026

"Imagine TRPM8 as a microscopic thermometer inside your body," said Hyuk-Joon Lee, a postdoctoral fellow in Seok-Yong Lee's laboratory at Duke University.

From Science Daily • Mar. 8, 2026

She studied the time on her watch, then pulled the thermometer out of my mouth.

From "Aristotle and Dante Discover the Secrets of the Universe" by Benjamin Alire Saenz

Related Words

• instrument
• thermostat