domain	the set of all possible inputs of a function which allow the function to work
excluded value	a value for a variable that is not allowed in an expression, such as a variable in a rational expression that would make the denominator equal zero
least common denominator	the smallest number or expression that is a multiple of all the denominators in a group of fractions or rational expressions
least common multiple	the smallest number or expression that is a multiple of a group of numbers or expressions
prime factorization	the process of breaking a number down into its prime factors
rational expression	a fraction with a polynomial in the numerator and/or denominator