o
Function: many-one( Not injective)
o Function that is not one-one is many-one.
Function: onto( or surjective)
A function f: X → Y is said to be onto( or surjective), if every element of Y is the image of some element of X under f, i. e., for every y ∈ Y, there exists an element x in X such that f( x) = y.