A function is a special type of relation between inputs and outputs. The key characteristic is that each input has exactly one output. Think of it like a machine: you put in a number, and it gives you exactly one result based on a specific rule.
Functions have important properties. The domain is the set of all possible input values. The range is the set of all possible output values. The key property of a function is that each input in the domain maps to exactly one output in the range.
To summarize: A function is a mathematical relationship where each input has exactly one output. Understanding domains and ranges helps us work with functions effectively. Functions are fundamental tools in mathematics, science, and engineering.