A fungus is an organism that can grow on living and nonliving things. Fungi (the plural of fungus) include many types of organisms including yeasts, mold, and mushrooms. Fungi that cause problems for people include yeasts and molds and other types of fungi.
In some situations, fungi can infect and damage tissue, such as skin, hair, or nails. Fungi also may be involved in infections throughout the body, such as in the central nervous system or the bloodstream.