operation of combining two functions by using the output of one as the input for the other
relation in which each element of the domain corresponds to exactly one element of the range
test that uses horizontal lines to determine whether a function is one-to-one. If any horizontal line intersects the graph in more than one point, the graph is not one-to-one.
result of switching the inputs and outputs of a function when the result is also a function. The composition of a function and its inverse is the identity function.