AHD

AHD or Ahd may refer to:

• Audio High Density, an audio-only version of the Video High Density videodisc format
• Acoustic Hailing Device, an audio device capable of providing high acoustic output at significant distance
• Australian Height Datum, a geodetic datum for altitude measurement in Australia
• National Rail Station Code AHD: Ashtead railway station, Ashtead, Surrey, England
• Anthony Henday Drive, an expressway in Edmonton, Alberta

In linguistics:

• Althochdeutsch (Ahd.), the German name for Old High German, the earliest stage of the German language
• The American Heritage Dictionary of the English Language

In medicine:

• Advance Health Directive, an Australian legal document
• Alveolar hydatid disease, a parasitic disease