Encyclopedias, Almanacs, Transcripts, and Maps
- Australian Toadlets and Water Frogs (Myobatrachidae)
- Australian Warblers (Acanthizidae)
- Australo-American Sideneck Turtles (Chelidae)
- Austronesian languages
- autochrome
- Automobile Emissions
- Avahis, Sifakas, and Indris (Indriidae)
- Avian Flight
- Avian Migration and Navigation
- Avian Song
- Aviation Fuel
- Avraham ben David of Posquières
- Axis Mundi
- Aye-Ayes (Daubentoniidae)
- Ayub Khan, Muhammad
- Āyurveda
- Aztec Religion
- Baal, Jan van
- Baba Yaga
- Babblers (Timaliidae)