Pathogen : path·o·gen
Function: noun
An agent that causes disease, especially a living microorganism such as a bacterium or fungus.
A pathogen (literally "birth of pain" from the Greek pa?????e?a ) is a biological agent that can cause disease to its host . A synonym of pathogen is " infectious agent". The term "pathogen" is most often used for agents that disrupt the normal physiology of a multicellular animal or plant. However, pathogens can infect unicellular organisms from all of the biological kingdoms.
Protozoa
