| Advisory Committee on Antarctic Names | Advisory Committee on Antarctic Names |
| Advokat | Advokat |
| Adwaita | Adwaita |
| AdWords | AdWords |
| ADX Florence | ADX Florence |
| Adyguée | Adygea |
| Adyguéens | Adyghe people |
| Adynaton | Adynaton |
| Adèle | Adela |
| Adèle de Champagne | Adèle of Champagne |
| Adèle de Flandre | Adela of Flanders |
| Adèle de Savoie | Adelaide of Maurienne |
| Adékambi Olufadé | Adékambi Olufadé |
| Adélard de Bath | Adelard of Bath |
| Adélard de Corbie | Adalard of Corbie |
| Adélaïde | Adelaide |
| Adélaïde City FC | Adelaide City |
| Adélaïde de Bourgogne | Adelaide of Italy |
| Adélaïde de France | Marie Adélaïde of France |
| Adélaïde de Frioul | Adelaide of Paris |
| Adélaïde de Louvain | Adeliza of Leuven |
| Adélaïde de Montferrat | Adelaide del Vasto |
| Adélaïde de Normandie | Adelaide of Normandy |
| Adélaïde de Saxe-Meiningen | Adelaide of Saxe-Meiningen |
| Adélaïde de Suse | Adelaide of Susa |
| adénine | adenine |
| adénomyose | adenomyosis |
| Adénopathie | Lymph node involvement |
| Adénosine diphosphate | Adenosine diphosphate |
| Adénosine monophosphate cyclique | Cyclic adenosine monophosphate |
| Adénosine triphosphate | adenosine triphosphate |
| adénoviral | adenoviral |
| adénovirus | adenovirus |
| adénoïde | adenoid |
| Adénylate cyclase | Adenylate cyclase |
| Adéodat | Adeodatus |
| Adéodat Ier | Pope Adeodatus I |
| Adéodat II | Pope Adeodatus II |
| adéquat | suitable |
| adéquatement | adequately |
| adéquation | sufficiency |
| Adûnaic | Adûnaic |
| Adıyaman | Adıyaman Province |
| AE | AE |
| Aechmophorus | Aechmophorus |
| Aed Oirdnide mac Neill | Áed Oirdnide |
| Aedermannsdorf | Aedermannsdorf |
| Aedes | Aedes |
| Aedes aegypti | Aedes aegypti |
| Aedes albopictus | Asian tiger mosquito |
