**Definition:**A function is a preset formula in Excel. Like formulas, functions begin with the equal sign (

**=**) followed by the function's name and its arguments. The function name tells Excel what calculation to perform. The arguments are contained inside round brackets.

For example, the most used function in Excel is the SUM function, which is used to add together the data in selected cells. The SUM function is written as -

= SUM ( D1 : D6 )Here the function adds the contents of cell range D1 to D6 and displays the answer in cell D7.

**Examples:**