Onto Function is one of the many types of functions defined based on the relationship between its domain and codomain. For any function to be onto, it needs to relate two sets with a very specific mapping between elements, meaning that each element of the codomain has at least one element in the domain as its pre-image. In simple words, for any function, if all the elements of the codomain are mapped to some element of the domain, then the function is said to be an onto function.

In this article, we will discuss the concept of onto or surjective function in detail including its definition, example, and many more. We will also discuss key differences between one one, onto and into functions as well.

https://www.geeksforgeeks.org/maths/onto-functions/

An onto function, also known as a surjective function, is a special type of mathematical rule that connects two sets, let's call them Set A and Set B. In an onto function, every element in Set B has a partner in Set A. This means that the function covers all the elements in Set B and there are no leftovers in Set B without a matching element in Set A.