# Injective and Surjective Functions

Learn about special kinds of functions like injective and surjective functions.

## Injective functions

A function is **injective** if every element of the domain maps to a unique element of the codomain. This means that if a function is injective, no two elements from the domain can map to the same element in the codomain. For example, if we consider **one-to-one function**. To define an injective function, the codomain must have at least as many elements as are there in the domain.

### Examples

Take the following sets:

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