Plural of effluvium; invisible streams of particles or vapors emanating from a substance, often thought to carry odor or influence.
From Latin effluvium, from effluere (to flow out), combined with -um suffix. The plural can be formed as effluviums (English) or effluvia (Latinized). Used in medieval natural philosophy to explain odors and disease transmission.
Medieval doctors used the concept of effluviums to explain how diseases spread through 'bad air'—they weren't entirely wrong, since airborne particles do carry pathogens, but they imagined invisible vapors with almost magical properties.
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