decayde‧cay1 /dɪˈkeɪ/ ●●○ verb1[intransitive, transitive]DECAY to be slowly destroyed by a naturalchemicalprocess, or to make something do thisHer body was already starting to decay.Most archaeological finds are broken, damaged, or decayed.decaying organic matterRegisterIn everyday English, people usually say rot rather than decay when talking about food:There was a smell of rotting vegetables.2[intransitive]DECAY if buildings, structures, or areas decay, their condition gradually becomes worseHundreds of historic buildings are being allowed to decay.Britain’s decaying inner cities3[intransitive]LESS if traditionalbeliefs, standards etc decay, people do not believe in them or support them anymore syn declineIn Orthodox Europe, mass religion seems to have decayed less.THESAURUSdecay to be slowly destroyed by a natural chemical process – use this especially about natural things such as wood or plants, or about teethThe leaves decay and enrich the soil.He had bad breath and decaying teeth.The fabric slowly began to decay. rot to decay. Rot is less formal than decay and is more common in everyday EnglishThe fruit was left to rot on the ground.rotting teethMost of the wood under the paint had rotted.the smell of rotting vegetation (=decaying leaves and plants)go off British English if food goes off, it starts to smell bad and is no longer be safe to eatI think the milk’s gone off.The meat smells as if it's gone off.spoil if food spoils, it starts to decay, so that it is no longer safe to eat. Spoil is more formal and is less common in everyday British English than go offFood left in the sun will quickly start to spoil.go mouldy British English, moldy American English to begin to have a softgreen or blacksubstancegrowing on the surface of the food, so that it is not good to eat anymoreUgh, the cheese has gone mouldy!decompose formal to decay – use this especially about dead plants or fleshleaves decomposing on the forest floorputrefy formal to decay and have a very bad smell – use this especially about flesh or plantsAfter two days, the body was already beginning to putrefy.putrefying meatbiodegrade to decay naturally into substances that do not harm the environment – use this especially about man-madematerials and chemicalsUnlike many other materials, plastic does not biodegrade.→ See Verb table
decaydecay2 ●●○ noun [uncountable]1DECAYthe natural chemical change that causes the slowdestruction of somethingold cars in various stages of decaytooth decay2DESTROYthe gradual destruction of buildings, structures etc because they have not been cared forpoverty and urban decayfall into (a state of) decayDuring the war, the area fell into decay.3LESSthe gradual destruction of ideas, beliefs, social or political systems etcmoral decayCOLLOCATIONSverbscause decayBacteria stick to food and cause decay.prevent decayYou can use a preservative on the wood to prevent further decay.ADJECTIVES/NOUN + decay tooth/dental decayEating too much sugar causes tooth decay.natural decayEverything in our environment is subject to natural decay.phrasesthe process of decayThe natural processes of decay gradually destroys archaeological sites.a sign of decayI couldn't see any signs of decay on the fruit.