In mathematics, a function is a relationship or rule that assigns each input exactly one output. This means that for every value in the input set (often referred to as the domain), there is a unique corresponding value in the output set (often referred to as the range).
In the context of the provided table, each day of the week serves as an input, and the number of children in the car serves as the output. The table shows a function because each day of the week (Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday) is associated with exactly one number of children. There are no days that share the same number of children as another day, ensuring that every input has a unique output. Therefore, this fulfills the definition of a function.