Wiktionary
avogadro's number
n. (context chemistry physics English) The number of atoms present in 12 grams of isotopically pure carbon-12, being 6.0221415 x 1023. By definition, the number of elementary entity (atoms or molecules) comprising one mole of a given substance.
Usage examples of "avogadro's number".
In a few days, I came up with a complete set of weights and measures, all based either on our yard, or in the case of my electrical standards, on Avogadro's number.
I would remind you that there is no religious debate about Avogadro's number, or Planck's constant, or the functions of the pancreas.