👉 In mathematics, a grouper is a function that takes two numbers as input and returns a number. The output of a grouper is also called its result or output. For example, if we have the function `f(x) = x^2`, then `f(3)` would return 9 because when you substitute 3 into this function, it will give you 9. So in summary, a grouper is a function that takes two numbers as input and returns a number.