| Anthropology (Human beings and their way of life) |
Aphnology |
| Apiology |
Arachnology |
| Arachnology (Spiders) |
Archaeology |
| Archaeology (Human Antiquities) |
Archelogy |
| Archology |
Arctophily |
| Areology |
Aretaics |
| Aristology |
Arthrology |
| Astacology |
Astheniology |
| Astrogeology |
Astrology |
| Astrology (The influence of planets on life) |
Astrometeorology |
| Astronomy |
Astrophysics |
| Astroseismology |
Atmology |
| Audiology |
Audiology (Hearing) |
| Autecology |
Autology |
| Auxology |
Avionics |