## What Is a Function?

Functions express a relationship between an input and an output. If you put a number in to a function, another number will come out.## Dictionary Definition

The Merriam-Webster dictionary defines a function as "a mathematical correspondence that assigns exactly one element of one set to each element of the same or another set."## Functions As Equations

Functions are usually expressed as an equation, where the relationship between the input and output is shown. The equation below shows a function, which will be called**f**.

The equation shows that the output of the function, which is denoted

**f(x)**(said as "f of x"), is related to the input of the function, which is denoted

**x**. The function takes the input

**x**and adds 1 to it.

## The Curriculum

The lessons are grouped into mini-curriculum to help you organise your learning. A brief description is given for each mini-curriculum. Click the**MORE**button to learn more.

## Functions

Functions relate inputs to outputs. An equation is usually used to describe this relationship.
Functions can be thought of as a mapping. An input is mapped to an output. If you put a number in, the function relates it to another number.
In this mini-curriculum, you will learn about functions.

## Plotting Functions

Functions can be plotted on a graph.
The graph shows the relationship between the input (along the horizontal x-axis) and the output (up the vertical y-axis).
In this mini-curriculum, you will learn about plotting functions.

## Composite Functions

Composite functions combine functions, so that the output of one function becomes the input of another.
In this mini-curriculum, you will learn about composite functions.

## Inverse Functions

The inverse of a function reverses that function.
If a function relates an input to an output, the inverse function relates the output back to the input.
In this mini-curriculum, you will learn about inverse functions.