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• Kelvin
  Kelvin

  noun

  William Thomson, 1st Baron, 1824–1907, English physicist and mathematician.
• kelvin
  kelvin

  noun

  the basic SI unit of thermodynamic temperature; the fraction 1/ 273.16 of the thermodynamic temperature of the triple point of water

Kelvin

American  

[kel-vin] / ˈkɛl vɪn /

noun

1. William Thomson, 1st Baron, 1824–1907, English physicist and mathematician.

2. (lowercase) the basic unit of temperature in the International System of Units (SI), formally defined to be approximately 1/273 of the triple point of water. K

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adjective

1. Thermodynamics. noting or pertaining to an absolute scale of temperature Kelvin scale in which the degree intervals are equal to those of the Celsius scale and in which absolute zero is 0 degrees Kelvin and the triple point of water has the value of approximately 273 degrees Kelvin.

2. Also Kelwin a male given name.

Kelvin ¹ British  

/ ˈkɛlvɪn /

noun

1. William Thomson, 1st Baron Kelvin. 1824–1907, British physicist, noted for his work in thermodynamics, inventing the Kelvin scale, and in electricity, pioneering undersea telegraphy

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kelvin ² British  

/ ˈkɛlvɪn /

noun

1.  K.  the basic SI unit of thermodynamic temperature; the fraction 1/ 273.16 of the thermodynamic temperature of the triple point of water

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kelvin ¹ Scientific  

/ kĕl′vĭn /

1. The SI unit used to measure temperature, the basic unit of the Kelvin scale. A difference of one degree Kelvin corresponds to the same temperature difference as a difference of one degree Celsius.

2. See Table at measurement See also absolute zero

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Kelvin ² Scientific  

1. British mathematician and physicist known especially for his work on heat and electricity. In 1848 he proposed a scale of temperature independent of any physical substance, which became known as the Kelvin scale.

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Explanation

A kelvin is a unit for measuring temperature. The kelvin scale is based on absolute zero, the coldest possible measurement, so there is no such thing as a negative temperature in kelvins. The Celsius scale is based on kelvins, but the two scales differ in that kelvins measure an absolute temperature, based on a zero that can literally not get any colder. While temperature isn't commonly measured in kelvins outside the science lab, it's a vital way of calculating temperature for scientists. The kelvin is named after the Irish-Scottish physicist Sir William Thompson, also known as Lord Kelvin.

Example Sentences

Pasadena, for example, is slowly replacing sodium lights with LEDs, but with a Kelvin ceiling of 2,700 to 3,000.

From Los Angeles Times • May 8, 2026

The 30-year-old Kenyan crossed the line to win in one hour 59 minutes 30 seconds, more than one minute faster than the late Kelvin Kiptum's previous record of 2:00:35, set in 2023.

From BBC • Apr. 26, 2026

Kenya’s Sabastian Sawe finished in 1:59:30, obliterating the previous record of 2:00:35 set at the 2023 Chicago Marathon by Kenyan Kelvin Kiptum.

From The Wall Street Journal • Apr. 26, 2026

They operate at temperatures as high as 13 Kelvin, compared with about 1 Kelvin for aluminum based platforms.

From Science Daily • Feb. 25, 2026

The German scientist Hermann von Helmholtz, no intellectual slouch himself, wrote that Kelvin had by far the greatest "intelligence and lucidity, and mobility of thought" of any man he had ever met.

From "A Short History of Nearly Everything" by Bill Bryson