Leo A. Aroian, The Probability Function of the Product of Two Normally Distributed Variables, The Annals of Mathematical Statistics, Vol. 18, No. 2 (Jun., 1947), pp. 265-271 ...

This is called function notation and is just another way of expressing the relationship between two variables. Therefore, in general y = f (x).

Educational Studies in Mathematics, Vol. 95, No. 2 (June 2017), pp. 181-202 (22 pages) Recent research suggests that children in elementary grades have some facility with variable and variable ...

Functions are written in function notation with the name of the function (usually f or g), a variable written in brackets and an expression.