mold
n. C / Un. a type of fungus that grows on old food or in damp places. It often looks like green, black, or white fuzzy spots.
n. a growth of fungus that occurs on organic matter in moist conditions, typically causing decay. Often used in the plural when referring to multiple types or widespread growth.
There is green mold growing on the old bread.
The landlord had to hire a professional team to remove the black mold from the bathroom walls.
While some varieties of mold are responsible for spoiling food, others are essential for the production of certain cheeses and life-saving antibiotics like penicillin.
From Middle English molde (“mold, cast”), from Old French modle, mole, from Latin modulus, from Latin modus. Doublet of module, modulus, and model.
From Middle English mowlde, noun use and alteration of mowled, past participle of mowlen, moulen (“to grow moldy”), from Old Norse mygla (compare dialectal Danish mugle), from Proto-Germanic muglōną, diminutive and denominative of mukiz 'soft substance' (compare Old Norse myki, mykr (“cow dung”)), from Proto-Indo-European *mewk- (“slick, soft”). More at muck and meek.
From Middle English molde, from Old English molde, from Proto-Germanic muldō (“dirt, soil”) (compare Old Frisian molde, Middle Dutch moude, Dutch moude, obsolete German Molte, Norwegian Bokmål mold, and Gothic 𐌼𐌿𐌻𐌳𐌰 (mulda)), from Proto-Indo-European ml̥h₂-téh₂ (compare Ashkun mič, Kamkata-viri muři, mřey, mřëi, Prasuni mire, Waigali muk, all meaning "clay").
From Middle English molde (“top of the head”), from Old English molda, molde, from Proto-West Germanic moldō, from Proto-Indo-European ml̥Hdʰṓ; exactly parallel to Sanskrit मूर्धन् (mūrdhán).
Uncountable when referring to the substance generally; countable when referring to specific biological types.