formula unit: Meaning and Definition of

for'mula u"nit

Pronunciation: [key]
— Chem. Chem.
  1. (of an ionic compound that does not form molecules, as most salts) the chemical formula with the least number of elements out of the set of empirical formulas having the same proportion of ions as elements: NaCl is the formula unit for the ionic compound sodium chloride.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.