Meaning of common denominator

com'mon denom'inator

Pronunciation: [key]
  1. a number that is a multiple of all the denominators of a set of fractions.
  2. a trait, characteristic, belief, or the like common to or shared by all members of a group: Dedication to the cause of freedom was the common denominator of the American revolutionaries.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.