The main differences between a built-in function and a method are:

The language also has a modest standard library of built-in functions.

This language has a library of about 120 built-in functions.

The programmer can pass arguments to one of many built-in functions, and a value may be returned.

This allows built-in functions and others to be used as if they threw exceptions.

The built-in function is often dangerous when used on completely untrusted data.

Changing so that it is a built-in function, not a statement.

It has more than 100 built-in functions for math, finance, statistics and business.

Numbers '09 contains 262 built-in functions that can be used in formulas.

Additionally S2K's own set of built-in functions was rather limited.