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

See Examples For:

thermometer thermometers

Inside, the temperature is 23C while outside the thermometer read 30C on Wednesday.

From Barron's ● Jun. 26, 2026

They generally sleep best when their bedroom temperature is between 16C and 20C - use a room thermometer to check.

From BBC ● Jun. 22, 2026

He gave a tour of his room in the quarantine center on Instagram, showing the fridge, smart TV and thermometer he was given for temperature checks.

From The Wall Street Journal ● May 12, 2026

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

Layla disappeared into the bathroom and came back with a digital thermometer.

From "Ivy Aberdeen’s Letter to the World" by Ashley Herring Blake

Today, gallium is widely used in semiconductors, telecommunications equipment, LEDs, laser diodes, solar panels, high performance computing, the aerospace and defense industries, and as a safer alternative to mercury in thermometers.

From Science Daily ● Jul. 9, 2026

One worker said: "We don't seem to have enough thermometers."

From BBC ● Jun. 16, 2026

Late Friday, firefighters had been relying on drone-based thermometers to estimate the temperature inside the failing tank, which gave a reading of 61 degrees, with 50 degrees being the goal.

From Los Angeles Times ● May 23, 2026

Two people in the area fainted as thermometers showed the temperature hitting 97 degrees.

From The Wall Street Journal ● Nov. 21, 2025

One of his early ideas was one of the first thermometers, which worked ‘upside down’ to modern eyes.

From "The Scientists" by John Gribbin

Related Words

• instrument
• thermostat