“A function describes a relationship between input and output values.” “The domain is the set of x-values.” “The range is the set of y-values”. “If an element of a function’s range is paired with exactly one element of domain, then the function is a one-to-one function. “ Real world situations often have a constraint, a condition a solution must satisfy, such as when dealing with time you can’t have negative numbers. A continuous function is graphed with a line or unbroken curve. A discontinuous function is not continuous. A discrete function is a discontinuous function in which the points aren’t connected.