De*nom"i*na`tor (?), n. [Cf. F. d'enominateur.]
One who, or that which, gives a name; origin or source of a name.
This opinion that Aram . . . was the father and denomination of the Syrians in general.
Sir W. Raleigh.
That number placed below the line in vulgar fractions which shows into how many parts the integer or unit is divided.
⇒ Thus, in denominator, showing that the integer is divided into five parts; and the numerator, 3, shows how many parts are taken.
That part of any expression under a fractional form which is situated below the horizontal line signifying division.
⇒ 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. )
© Webster 1913.