GNU Collaborative International Dictionary of English

Found one definition

1.       
   Denominator , n. [Cf. F. dénominateur.]
   One who, or that which, gives a name; origin or source of a name.
   1913 Webster
   This opinion that Aram . . . was the father and denomination of the Syrians in general.
   Sir W. Raleigh.
   
   1913 Webster
   (Arith.) That number placed below the line in common fractions which shows into how many parts the integer or unit is divided.
   1913 Webster
   ☞ Thus, in ⅗, 5 is the denominator, showing that the integer is divided into five parts; and the numerator, 3, shows how many parts are taken.
   1913 Webster
   (Alg.) That part of any expression under a fractional form which is situated below the horizontal line signifying division.
   1913 Webster
   ☞ In this sense, the denominator is not necessarily a number, but may be any expression, either positive or negative, real or imaginary.
   Davies & Peck (Math. Dict.)
   
   1913 Webster
   common denominator a number which can divide either of two or more other numbers without leaving a remainder in any of the divisions; as, 2 and 4 are common denominators of 12 and 28.. -- greatest common denominator the largest common denominator of two or more numbers; as, 9 is the greatest common denominator of 18 and 27..
   PJC