Parasitism - A close relationship between two organisms in which one organism, the parasite, benefits at the expense of the host organism.⏎
Protozoa - A taxonomic group of single-celled microorganisms that live in almost every kind of habitat and include some pathogenic parasites of humans and other animals. ⏎
Organism - A living being that can reproduce, grow, react to external stimuli, and maintain its internal equilibrium.⏎
Prion - A causative agent of infectious disease that is composed primarily of protein.⏎
Nanometer - A unit of length equal to one one-billionth (1 x 10-9) of a meter.⏎