In Technology:

• Adobe Digital Negative, a RAW image format designed by Adobe Systems
• Application Delivery Network, a suite of technologies that, when deployed together, provide application availability, security, and acceleration.
• Autodesk Developer Network, a program for developers working with Autodesk software.
• Aircraft Data Network, an ARINC specification proposing data networking standards for use in commercial aircraft installations

In Sciences:

• Obscure Auditory Dysfunction, an auditory disability with clinically a “normal” hearing threshold

In Politics:

• Acción Democrática Nacionalista (Nationalist Democratic Action), a political party of Bolivia
• Alleanza Democratica Nazionale (National Democratic Alliance), a former political party of Italy

In Medias

• Allgemeiner Deutscher Nachrichtendienst, the official news agency of East Germany
• Anchorage Daily News
• ADN, a Spanish free daily newspaper

Other uses:

• Abbreviated Dialling Number
• Andes Airport, Colombia, from its IATA airport code
• any day now in internet slang
• Ardrossan Town railway station, United Kingdom, from its National Rail code