1. A general term used to denote a class of 
microbes including mushrooms, yeasts and molds. 2. Fungi, which were once classified as plants, have since been reclassified as unmoving organisms that lack chlorophyll. Mycologists (scientists working with fungi) estimate that there are 100,000 species of fungi, ranging from baker's yeast to dermatophytes (fungi that cause ringworm and athlete's foot) to potentially invasive species such as 
Candida albicans and Aspergillus. As many as 150 of these organisms have now been linked to animal or human diseases.