Function - GCSE Maths Definition

In GCSE Maths, a "function" is a special relationship between two sets of numbers or things, where each input (or starting number) has exactly one output (or resulting number). You can think of a function like a machine: you put a number in, and following the function's rule, a specific number comes out. For example, if the function rule is to double the number, and you put in 3, the machine gives you 6. Functions are important because they help us understand and predict how different values are connected to each other in maths and in real life.