## Functions

Excel has hundreds of built-in Functions installed by default. Possibly two of the most popular Functions (and easiest to use) are:

- =SUM()

The SUM function simply adds together numbers and returns their total sum. - =COUNT()

The COUNT function simply counts numbers in any given range of cells.

*So a Function is a single predefined formula that is built into Excel.*

## Formulas

A formula is a statement that contains one or more functions. If properly constructed a formula will return the result you want.

### Formula and Function Rules

There are only two rules when using functions to create formulas in Excel and these are:

- All formulas and functions must begin with a = (equal sign).
- For every open parenthesis (brackets) there must be a closing parenthesis.

*Don't confuse point 2 as meaning all formulas must have open and closing parenthesis, as this not always true.*

What is does mean is, all of Excels built-in Functions use at least one set of open and closing parenthesis.

### ðŸ’¡ TIP

Whenever you type in a function name, always type it in lower case.

- The reason for this is that if you have spelt the Function name correctly, Excel will automatically convert it to UPPERCASE.
- It is a quick and handy error checking tool. ðŸ˜Š

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