# kelvin

/ˈkɛɫvən/ (US) · /kˈɛlvɪn/ (UK)

Source: https://englishreference.com/word/kelvin
Updated: 2026-08-27

## Senses

### 1. scientific temperature unit

noun · CEFR C1 · Technical

a unit of temperature used in science where zero is the coldest possible temperature.

For teachers: the SI base unit of thermodynamic temperature, defined by the Boltzmann constant; zero kelvin represents absolute zero.

- Scientists measured the liquid nitrogen at 77 kelvins during the experiment.
- At temperatures approaching zero kelvin, certain materials exhibit superconductivity, allowing electrical current to flow without resistance.

Usage: The word is not capitalized when referring to the unit, and it does not take the word 'degree'.

### 2. color temperature

noun · CEFR C2 · Technical

a way to describe how 'warm' or 'cool' the light from a bulb looks.

For teachers: a measure of the color character of a light source, based on the temperature of an ideal black-body radiator.

- I prefer light bulbs with a lower kelvin rating for a cozy, yellow glow.
- Photographers often adjust their white balance to match the kelvin value of the ambient lighting to ensure accurate color reproduction.

## Examples

- Water freezes at about 273 kelvins.
- The laboratory equipment must be kept at a temperature of exactly four kelvins for the experiment to work.
- While the Celsius scale is used for daily weather, physicists prefer the kelvin because it provides an absolute measurement where zero represents the total absence of thermal energy.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.