magazine or newspaper Assistant director, a film or television crew member Athletic director, the administrator of an athletics program Science and technology Biology and medicine Addison's disease, an endocrine disorder Adenovirus, viruses of the family Adenoviridae Alzheimer's disease, a neurodegenerative disease Anaerobic digestion, processes by which microorganisms break down biodegradable material Anti-diarrheal, medication which provides symptomatic relief for diarrhea Approximate digestibility, an index measure of the digestibility of animal feed Atopic dermatitis, form of skin inflammation Atypical depression, a type of depression Autosomal dominant, a classification of genetic traits Autonomic dysreflexia, a potential medical emergency Chemistry Adamantyl, abbreviated "Ad" in organic chemistry Sharpless asymmetric dihydroxylation, a type of organic chemical reaction Computing .ad, the top level domain for Andorra Administrative distance, a metric in routing Active Directory, software for the management of Microsoft Windows domains Administrative domain, a computer networking facility Analog-to-digital converter, a type of electronic circuit Automatic differentiation, a set of computer programming techniques to speedily compute derivatives AD16, the hexadecimal number equal to decimal number 173 Mathematics Adjoint representation of a Lie group, abbreviated "Ad" in mathematics Axiom of determinacy, a set theory axiom Physics Antiproton Decelerator, a device at the CERN physics laboratory Autodynamics, a physics theory Other uses in science and technology Active Disassembly, a technology supporting the cost-effective deconstruction of complex materials Transportation AD, IATA code for: Air Paradise, a defunct Indonesian airline Azul Brazilian Airlines Airworthiness Directive, an aircraft maintenance requirement notice Other uses ʿĀd, an ancient Arab tribe, mentioned in the Quran Aggregate demand, in macroeconomics Anno Diocletiani, an alternative year numbering system United States Academic Decathlon, a high school academic competition See also Anno Domini (disambiguation) BC (disambiguation) Domino (disambiguation) Dominus (disambiguation)