Worksheet functions have two parts: the name of the function and the argument(s) that follow. Function names—such as SUM and AVERAGE—describe the operation that the function performs. Arguments specify the values or cells to be used by the function.

For example, the function ROUND has the following syntax: =ROUND(number, num_digits) as in the formula =ROUND(M30,2). The M30 is a cell reference entered as the number argument of the value to be rounded. The 2 is the num_digits argument. The result of this function is a number (whatever M30 happens to be) rounded to two decimal places.

Parentheses surround function arguments. The opening parenthesis must appear immediately after the name of the function. If you add a space or some other character between the name and the opening parenthesis, the error value #NAME? appears in the cell.

Note: a few functions, such as PI, TRUE, and NOW have no arguments. (These functions are usually nested in other formulas.) Even though they have no arguments, they must be followed by an empty set of parentheses, as in =NOW( ).

When you use more than one argument in a function, you separate the arguments with commas.

For example, the formula =PRODUCT(C1,C2,C5) tells Excel to multiply the numbers in cells C1, C2, and C5.

Some functions, like PRODUCT and SUM, take an unspecified number of arguments.

You can use as many as 30 arguments in a function, as long as the total length of the formula does not exceed 1,024 characters. However, you can use a single argument, or a range that refers to any number of cells in your worksheet, as a formula.

For example, the function =SUM(A1:A5,C2:C10,D3:D17) has only three arguments but actually totals the values in 29 cells. (The first argument, A1:A5, refers to the range of five cells from A1 through A5, and so on.) The referenced cells can, in turn, also contain formulas that refer to more cells or ranges.