JaDEX is only a piece of software, it needs dictionary data in order to be useful. If you have just downloaded JaDEX and are running it for the first time, you will need to connect to the internet and run the update procedure in order to download the database from the DEX online site.

• Go to the File menu
• Select the Update item
• Press the Start button to initiate the procedure
• The whole procedure will download over 100Mb of data and will then parse it into the JaDEX database, so it will take a while (4 minutes on my MacBook Pro): when it finishes press the Close button and start looking up words!

You can re-run the update procedure anytime you want after the first time in order to get new or updated entries from the web site. The software will NOT download the whole database again, but only the recent changes or additions.