De*nom"i*na`tor (?), n. [Cf. F.
dénominateur.] 1. 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.
2. (Arith.) That number placed below
the line in vulgar fractions which shows into how many parts the
integer or unit is divided.
&fist; 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.
3. (Alg.) That part of any expression
under a fractional form which is situated below the horizontal line
&fist; 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. )