Explain in more detail about one to one and onto function?

For one to one function each element in the domain is mapped on to an one and only one element in the co-domain.

The could be some elements in the co-domain that are not being used.

For a function to be one to one, then for


if and only if



For an onto function all the elements in the co-domain must be used up.

In order words, the

The condition is

Meaning each