Onto function: Learn what an onto function is

Learn what an onto function is, how to check if a function is onto , and how to find the number of onto functions. See examples, graphs, and FAQs on onto functions. An onto function , also known as a surjective function , is a type of function where every element in the co-domain is mapped to at least one element in the domain. In other words, an onto function covers the entire codomain, ensuring that every possible output value is achieved by some input value. In mathematics, a surjective function (also known as surjection, or onto function / ˈɒn.tuː /) is a function f such that, for every element y of the function's codomain, there exists at least one element x in the function's domain such that f(x) = y.