Describe what a function is

an activity or purpose natural to or intended for a person or thing.

a relationship or expression involving one or more variables.

work or operate in a proper or particular way.

a thing dependent on another factor or factors.

a large or formal social event or ceremony.

fulfill the purpose or task of (a specified thing).

Answer: Function

Explanation: The reason some objects or a process that occurred in a system that developed through natural selection.