# Planck

/ˈpɫæŋk/ (US) · CEFR C2 · Noun

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

## Definition

a name used for very small measurements in physics. It refers to the smallest possible scales of energy, time, and space in the universe.

For teachers: Refers to the fundamental physical constants and scales derived by Max Planck, specifically the Planck constant (h). Often used as a modifier to describe the smallest meaningful units of measurement in quantum mechanics, such as Planck length or Planck time.

## Examples

- Scientists study the universe at the Planck scale.
- In quantum physics, the Planck constant relates the energy of a photon to its frequency.
- Theoretical physicists often encounter significant mathematical hurdles when attempting to reconcile general relativity with the extreme conditions found at the Planck length.

## Usage notes

- Usually functions as a proper noun or a modifier in scientific compound terms; when used as a unit of measurement, it is countable.

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