The quality or state of being foul; the condition of being dirty, disgusting, or morally corrupt.
From 'foul' + the noun-forming suffix '-ness,' dating to Old English. This suffix creates abstract nouns representing the essential quality or condition of an adjective.
The word 'foulness' is fascinating because it bridges two meanings—physical foulness (the stench of a swamp) and moral foulness (the wickedness of a deed)—and English has maintained both senses since medieval times without clearly separating them.
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