| Dactyliology |
Study of rings |
| Dactylography |
The study of fingerprints |
| Dactylology |
Study of sign language |
| Deltiology |
The collection and study of picture postcards |
| Demology |
Study of human behaviour |
| Demonology |
Study of demons |
| Dendrochronology |
Study of tree rings |
| Dendrology |
Study of trees |
| Deontology |
The theory or study of moral obligation |
| Dermatoglyphics |
The study of skin patterns and fingerprints |
| Dermatology |
Study of skin |
| Desmology |
Study of ligaments |
| Diabology |
Study of devils |
| Diagraphics |
Art of making diagrams or drawings |
| Dialectology |
Study of dialects |
| Dioptrics |
Study of light refraction |
| Diplomatics |
Science of deciphering ancient writings and texts |
| Diplomatology |
Study of diplomats |
| Docimology |
The art of assaying |
| Dosiology |
The study of doses |
| Dramaturgy |
Art of producing and staging dramatic works |
| Dysgenics |
The study of racial degeneration |
| Dysteleology |
Study of purposeless organs |