- Dactylography: It is the science of using fingerprints for identification purposes.
- Demography: The study of statistics such as births, deaths, income, population distribution, population density etc.
- Dentistry: The branch of medicine that deals with the diagnosis, treatment, and prevention of diseases related to teeth and oral cavities.
- Dendrology: This is the study of wooded plants.
- Dermatology: The study of skin structure and skin related diseases.
- Dynamics: The study of various forces, their actions on bodies, and the changes in the motion they produce.
- Ecology: The study of the relation of animals, plants and people to each other and to their surroundings.
- Economics: The science dealing with the production, distribution and consumption of goods and services.
- Endocrinology: It is the study of glands.
- Entomology: It is the study of insects.