Other forms: rotting, rotted, rots
Rot is the soft decay that destroys damp wood. Dry rot, wet rot, the rot has spread.
Dry rot is the serious one in buildings — a fungus that spreads through masonry and can consume a whole floor — and wet rot is the more localised damage where water keeps getting in. As a verb, to rot is what damp wood, fruit and teeth do. The rot set in is a fixed phrase for the moment a decline began. Note rotten, the adjective, and rot as a mild old-fashioned word for nonsense.
1nounrotThe soft decay that destroys damp wood.
“The rot had reached the joists before anybody looked.”
2verbdecayTo decay.
“The whole frame rotted from the bottom up.”
rot is decay.
Old English rotian is Germanic and gives both the verb rot and, through Norse, the adjective rotten. English rarely keeps two forms from one root this cleanly, and the pair has survived unchanged for a thousand years.
Proto-Germanic
*rutāną — to rot
Proto-West Germanic
*rotēn
Old English
rotian — to rot, become corrupted, ulcerate, putrefy
Middle English
roten
English, today
rot
Middle English roten, rotten, from Old English rotian (“to rot, become corrupted, ulcerate, putrefy”), from Proto-West Germanic rotēn, from Proto-Germanic rutāną (“to rot”).
Etymology from Wiktionary, CC BY-SA