Mildew is a kind of fungus that grows in damp environments. If you find a white, musty-smelling powder on a book that's been stored in the basement, it's probably mildew. Yuck!

Mildew and mold are closely related — mildew is a less harmful kind of fungus, though both can cause breathing problems. While mildew is almost always white, mold is darker and fuzzier. Since dampness causes mildew to spread, keeping things dry (possibly with the help of a dehumidifier or air conditioner) can help prevent it. The stickiness of plant mildew helps explain the word's etymology. It comes from a root meaning "honeydew."

Definitions of mildew

n a fungus that produces a superficial (usually white) growth on organic matter

show 5 types...
hide 5 types...
powdery mildew
any of various fungi of the genus Erysiphe producing powdery conidia on the host surface
downy mildew, false mildew
any of various fungi of the family Peronosporaceae parasitic on e.g. grapes and potatoes and melons
Peronospora tabacina, blue mold fungus
fungus causing a serious disease in tobacco plants characterized by bluish-grey mildew on undersides of leaves
Peronospora destructor, onion mildew
fungus causing a downy mildew on onions
Peronospora hyoscyami, tobacco mildew
fungus causing a downy mildew on growing tobacco
Type of:
an organism of the kingdom Fungi lacking chlorophyll and feeding on organic matter; ranging from unicellular or multicellular organisms to spore-bearing syncytia

n the process of becoming mildewed

mold, mould
Type of:
spoilage, spoiling
the process of becoming spoiled

v become moldy; spoil due to humidity

become affected with smut
affect or be affected with dry rot
Type of:
undergo a change; become different in essence; losing one's or its original nature

Sign up, it's free!

Whether you're a student, an educator, or a lifelong learner, can put you on the path to systematic vocabulary improvement.