It is part of a complex fraction.
The denominator.
denominator
It is the solidus line that separates the numerator from the denominator in a fraction
The part of a fraction that is below the line and that functions as the divisor of the numerator
fraction bar
The bottom of the fraction is the denominator.
It is the numerator.
The denominator in the unsimplified fraction.
It is the number below the division line.
fraction bar
It is a fraction if the number below the line is not zero. If the ABSOLUTE value of the number above the line is smaller than the ABSOLUTE value of the number below the line then it is a proper fraction. Otherwise it is an improper fraction.So, -7 is smaller than 2 but -7/2 is not a proper fraction because the absolute value of -7 (which is 7) is not smaller than the absolute value of 2 (= 2).
The denominator (the figure below the horizontal line)