### Introduction

In engineering there are many quantities that change their value as time changes. For example, the temperature of a furnace may change with time as it is heated. Similarly, there are many quantities that change their value as the location of a point of interest changes. For example, the shear stress in a bridge girder will vary from point to point across the bridge. A quantity whose value can change is known as a
**
variable
**
. We use
**
functions
**
to describe how one variable changes as a consequence of another variable changing. There are many different types of function that are used by engineers. We will be examining some of these in later Sections. The purpose of this Section is to look at the basic concepts associated with all functions.

#### Prerequisites

- have a thorough understanding of basic algebraic notation and techniques

#### Learning Outcomes

- explain what is meant by a function
- use common notations for functions
- explain what is meant by the argument of a function