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Our Word of the day is licit: not forbidden; lawful …

Definition of fungus

any of a group of unicellular, multicellular, or syncytial spore-producing organisms feeding on organic matter, including moulds, yeast, mushrooms, and toadstools: truffles are fungi but not mushrooms [mass noun]: fallen logs were overgrown with bright fungus [as modifier]: fungus infections like athlete’s foot
[mass noun] fungal infection (especially on fish): farmed fish often get fungus
[in singular] 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

Fungi lack chlorophyll and are therefore incapable of photosynthesis. Many play an ecologically vital role in breaking down dead organic matter, some are an important source of antibiotics or are used in fermentation, and others cause disease. The familiar mushrooms and toadstools are merely the fruiting bodies of organisms that exist mainly as a thread-like mycelium in the soil. Some fungi form associations with other plants, growing with algae to form lichens, or in the roots of higher plants to form mycorrhizas. Fungi are now often classified as a separate kingdom distinct from the green plants

late Middle English: from Latin, perhaps from Greek spongos (see sponge)

Make the plural of fungus by changing the -us ending to -i (as in the original Latin): fungi.

Definition of fungus in US English dictionary