Antisocial personality disorder, in psychology

Alpha Phi Delta (ΑΦΔ), a fraternity

Auditory processing disorder

Avoidant personality disorder, in psychology

Afferent pupillary defect

Avalanche photodiode, a device for counting photons

High speed transport, a type of vessel, from its United States hull classification symbol

Atlanta Police Department

Appledore railway station, from its National Rail code

Air passenger duty, an excise duty levied on passengers flying from UK airports

Austin Police Department