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.

---

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

---

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).

---

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

That can be vastly different from the reading on a thermometer.

From Los Angeles Times • Jun. 6, 2026

It is not impossible that parts of southern England and Wales could see the thermometer climbing even higher, into the mid-twenties Celsius.

From BBC • May 13, 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

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

From Slate • Apr. 17, 2026

The older lady was clearly unused to exercise; by the time she caught up with Penelope, her face looked like the scarlet top of a mercury thermometer just prior to bursting.

From "The Incorrigible Children of Ashton Place: Book I: The Mysterious Howling" by Maryrose Wood

Related Words

• instrument
• thermostat