# Glossary of Math Terminology

Decimal Fraction:  A fraction whose denominator is some power of 10 (i.e. a fraction whose denominator is 10 or 100 or 1000 etc).  Decimal fractions can easily be written without the denominator.  (i.e. 69/100 = 0.69   or   1,234/1,000,000 = 0.001234)

Denominator:  In a fraction the denominator is the number below the line (i.e in the fraction 69/100, 100 is the denominator).

Numerator:  In a fraction the numerator is the number above the line (i.e in the fraction 69/100, 69 is the numerator).

Arithmetic progression:  An adding or subtraction progression.  Counting (forwards or backwards) is an adding or subtraction progression.  0,1,2,3,4,5,6….. is an adding progression of One. 0,2,4,6,8,10…. is an adding progression of Two.   500, 375, 250, 125, 0,…. is a subtracting progression of One Hundred Twenty Five.

Geometric progression:  A multiplication or division progression.  1/4 1/2 1 2 4 8 16 32…. is a multiplication or ratio progression of Two.  Thus a geometric progression is a base number raised to successive powers.   1000, 100, 10, 1, 1/10 … is a division progression of 10, or ratio progression of 1/10 One Tenth.

Calculus:   The mathematical study of change – methods for jumping back and forth between rates of change and amounts of change.

Function:   A mapping equation, which calculates an output dependent quantity from an input independent variable.  y=2x is a doubling function.  Input 1 as the independent variable (x), and the dependent variable (y) is assigned the value 2.  Input x=2, and output value of y is equal to 4.  Input x=4, output y=8.  Input x=8, y=16.  Etc.  Etc…     [Note: Since y the dependent variable and x is the independent variable; y is thus a function of x and is  often written as y = f(x) ]

Exponential Function ( f(x) = ax ):   This is a function where the input variable is in the exponent. In the function y=ax, “y” is the dependent (or output) variable, “a” is a constant, and “x” is the independent (or input) variable, and in this equation “x” is the exponent in the equation.

Exponent:  The power to which a number is raised (e.g. when you square something, 2 is the exponent, and in the equation y=x3, 3 is the exponent).