# Planck's constant

## Noun

 Singular Planck's constant Plural none
1. (uncountable) Planck's constant is a measure of the size of a quantum, or the smallest 'piece' of energy that exists. It has a value ${\displaystyle h\approx 6.626\times 10^{-34}\ \mathrm {J} \cdot \mathrm {s} }$