Denominator

n.
  1. One who, or that which, gives a name; origin or source of a name.
  2. (Arith.) That number placed below the line in common fractions which shows into how many parts the integer or unit is divided.
  3. (Alg.) That part of any expression under a fractional form which is situated below the horizontal line signifying division.
    4. 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..