Parasitology
Parasitology is the study that deals with medically important parasites.
Definitions of terms used:

1. Parasite is an organism that lives on or inside of another orgnaism to detrimente of the hosts organism.

2. Host. Is an organism which support the parasite.

3. Parasitism. Is a form of symbiosis in which one organism benefits from the expenses of another organism usually of a different species.

4. Ecto parasite. Are parasites that live on the surface of the host such as lice and mice.

5. Endo parasite. Are parasites that live inside the host such as Giardia-lamblia, Ascaris lumbricoides.

6. Facultative parasite. Is an organism that exhibit both parasitic and non-parasitic mode of living in that it does not absolutely depend on the parasite mode of life. E.g Naegleria flowleria.

7. Trophezoite. Is the active feeding stage of a protozoa parasite

8. Cyst/Oocyst. Is the inactive feeding or infective form of a parasite.
   Reservoir. Is host that makes the parasite available for transmission to another host and is usually not affected by the infections.
   Obligate parasite. Is parasite that must always live in contact with its host.
   Definitive host. The host in which sexual reproduction takes place.
   Intermediate host. Host where/that harbours the larval stages of the parasite or where a sexual stage cycle of development occurs from.

Classification of Parasites: Parasites of medical importance are classified into two: Protozoa and Helminthes.

Mycology
Mycology is the study of fungi. Fungi are non-motile eukaryotic organisms which exist as saprophyte (derives its nourishments from decaying organic matter) or as parasite.

Virology
Virology is the study of viruses.