# What is a function?

What's a function?

A function is a special type of formula. You can think of a function as a pre-built formula with a specific purpose created to save time. Excel has hundreds of functions.

To introduce the idea of a function, we'll look at the SUM function. The SUM function is one of the most useful and widely used functions in Excel. It's purpose is to add things up.

let's take a look.

Here we have a worksheet with several labeled cell references. We have the individual cells B7 and D6, And the ranges F7:F9 and H8:H11.

Let's work through the formula examples.

As we saw in an earlier lesson, if we want to add B7 and D6 together, we can just type the formula B7 + D6.

And if we want to add cells in the range F7:F9, we can use F7+F8+F9

But this will get tedious quickly as the ranges we are adding get bigger. What we really need is a way to sum ranges directly. What we need, is the SUM function.

To use the SUM function, type an equal sign, the word SUM, and an open parentheses. Then, we can then simply select the F7:F9 range, close the parentheses, and press enter. Excel calculates the result.

We can do the same thing for range H8:H11.

The SUM function takes one or more arguments, which is just a fancy way of saying inputs. Because the SUM function can handle multiple arguments we can even sum both of these ranges in the same formula.

You can see that the SUM function is an easier way to add ranges, compared to building your own formula.