An example of a U.S. classified document; page 13 of a United States National Security Agency report on the USS Liberty incident, partially declassified and released to the public in July 2003. The original overall classification of the page, Top Secret code word UMBRA, is shown at top and bottom.
The Data Analysis Expressions (DAX) language is a formula language that allows users to define custom calculations in calculated columns and measures. DAX includes some of the functions that are used in Excel formulas, and additional functions that are designed to work with relational data and perform dynamic aggregation.
So what is DAX then? DAX stands for Data Analysis Expression. It is a special language we use to create measures in Power Pivot. Although it is a special language, it looks exactly like our regular Excel formulas. That means you can easily learn the DAX basics and create measures in no time. Think of DAX as Excel Formula ++. An upgraded version of Excel formulas that can handle power pivot data and give you the calculations you want.