- Ashkenazi, Ẓevi Hirsch ben Jacob, -17181
- Assumption of the Blessed Virgin Mary1
- Astrolabes15
- Astrology18
- Astrology, Arab8
- Astrology, Iranian1
- Astronomical instruments6
- Astronomy66
- Astronomy, Arab25
- Astronomy, Arab--Tables1
- Astronomy, Greek2
- Astronomy, Medieval10
- Astronomy--Tables2
- Athīr al-Dīn al-Abharī, al-Mufaḍḍal ibn ʻUmar, -1265. Hidāyat al-ḥikmah2
- Attila, -4531
- Augsburg Confession1
- Augustine, of Hippo, Saint, 354-4305
- Augustinians3
- Aurispa, Giovanni, approximately 1376-14591
- Austria--Lambach (Upper Austria)1