Definition:

The study of organisms which use other organisms as their living environment. Medical parasitology is concerned mainly with the larger, usually visible, parasites of humans such as the various worms and the external parasites (ectoparasites). Bacteria, viruses and protozoa, although parasites, are so important as to require separate disciplines and are not normally included in medical parasitology.

Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question, but by their way of life. This means it forms a synthesis of other disciplines, and draws on techniques from fields such as cell biology, bioinformatics, biochemistry, molecular biology, immunology, genetics, evolution and ecology.