An Etymological Dictionary of Astronomy and Astrophysics

The number of units in one → mole of any → substance (defined as its → molecular weight in grams), equal to 6.022 140 857 × 10²³. The units may be electrons, atoms, ions, or molecules, depending on the nature of the substance.

Etymology (EN): Named after Amedeo Avogadro (1776-1856), whose law allowed other physicists to calculate Avogadro’s number; → number.