fungus Any of a wide variety of organisms of the kingdom Fungi, which are unable to photosynthesize and which reproduce by means of spores and never produce cells with flagella. They include mushrooms, moulds, and yeasts. There are c.100,000 species. Fungi have relatively simple structures, with no roots, stems, or leaves. Their cell walls contain the polysaccharide chitin. The main body of a typical multicellular fungus consists of an inconspicuous network (mycelium) of fine filaments (hyphae), which contain many nuclei and may or may not be divided into segments by cross-walls. The hypha nuclei are haploid. The mycelia may develop spore-producing, often conspicuous, fruiting bodies, mushrooms and toadstools. Fungal parasites depend on living animals or plants: saprophytes utilize the materials of dead plants and animals, and symbionts obtain food in a mutually beneficial relationship with plants. Fungi feed by secreting digestive enzymes onto their food, then absorbing the soluble products of digestion. All three groups are of great importance to man. Many cause diseases in crops, livestock and humans (athlete's foot). Moulds and yeasts are used in the production of beer and cheese; some fungi, such as Penicillium, are sources of antibiotics.

fun·gus / ˈfənggəs/ • n. (pl. -gi / -jī; -gī/ or -gus·es) any of a group of unicellular, multicellular, or syncytial spore-producing organisms feeding on organic matter, including molds, yeast, mushrooms, and toadstools. ∎  fungal infection (esp. on fish). ∎  [in sing.] used to describe something that has appeared or grown rapidly and is considered unpleasant or unattractive: there was a fungus of outbuildings behind the house.

fungus (fung-ŭs) n. (pl. fungi) a simple organism (formerly regarded as a plant) that lacks the green pigment chlorophyll. Fungi include the yeasts, rusts, moulds, and mushrooms. Some species infect and cause disease in humans. Some yeasts are a good source of vitamin B and many antibiotics are obtained from the moulds (see penicillin). See also yeast.
—fungal adj.

fungus mushroom or the like XVI; spongy excrescence XVII. — L. fungus, perh. connected with Gr. sp(h)óggos, SPONGE.
So fungous XV. — L. fungōsus.

fungus See FUNGI.