# Kev

CEFR C2 · Noun

Source: https://englishreference.com/word/kev
Updated: 2026-08-15

## Definition

a very small unit of energy used by scientists to measure how fast tiny particles move. It is short for 'kilo-electronvolt'.

For teachers: a unit of energy equal to one thousand electronvolts, commonly used in particle physics and radiology to express the energy of X-rays or the kinetic energy of electrons. Often written as keV with a lowercase 'k' and uppercase 'V'.

## Examples

- The X-ray machine operates at 100 keV.
- Researchers measured the energy of the emitted photons and found they peaked at approximately 50 keV during the experiment.
- In high-energy physics, the precision of the detector allows for the identification of specific isotopes by measuring gamma-ray emissions that fall within the range of several hundred keV.

## Usage notes

- Usually written as the abbreviation 'keV'; the full term 'kilo-electronvolt' is rarely used in speech.

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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.