/ Dictionary / Index C common logarithm: Meaning and Definition of Find definitions for: com'mon log'arithm Pronunciation: [key] — Math. Math. a logarithm having 10 as the base. Also calledCf. natural logarithm. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. common-law marriage commonly Related Content Daily Word Quiz: nefarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language