I. de ‧ cay 1 /dɪˈkeɪ/ BrE AmE verb
[ Date: 1400-1500 ; Language: Old North French ; Origin: decaïr , from Late Latin decadere 'to fall, sink' ]
1 . [intransitive and transitive] to be slowly destroyed by a natural chemical process, or to make something do this:
Her body was already starting to decay.
Most archaeological finds are broken, damaged, or decayed.
decaying organic matter
In everyday English, people usually say rot rather than decay when talking about food:
There was a smell of rotting vegetables.
2 . [intransitive] if buildings, structures, or areas decay, their condition gradually becomes worse:
Hundreds of historic buildings are being allowed to decay.
Britain’s decaying inner cities
3 . [intransitive] if traditional beliefs, standards etc decay, people do not believe in them or support them any more SYN decline :
In Orthodox Europe, mass religion seems to have decayed less.
• • •
▪ decay to be slowly destroyed by a natural chemical process – use this especially about natural things such as wood or plants, or about teeth:
The 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 English:
The fruit was left to rot on the ground.
Most 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 eat:
I 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 off :
Food left in the sun will quickly start to spoil.
▪ go mouldy British English , moldy American English to begin to have a soft green or black substance growing on the surface of the food, so that it is not good to eat any more:
Ugh, the cheese has gone mouldy!
▪ decompose formal to decay – use this especially about dead plants or flesh:
leaves decomposing on the forest floor
▪ putrefy formal to decay and have a very bad smell – use this especially about flesh or plants:
After two days, the body was already beginning to putrefy.
▪ biodegrade to decay naturally into substances that do not harm the environment – use this especially about man-made materials and chemicals:
Unlike many other materials, plastic does not biodegrade.
II. decay 2 BrE AmE noun [uncountable]
1 . the natural chemical change that causes the slow destruction of something:
old cars in various stages of decay
2 . the gradual destruction of buildings, structures etc because they have not been cared for:
poverty and urban decay
fall into (a state of) decay
During the war, the area fell into decay.
3 . the gradual destruction of ideas, beliefs, social or political systems etc:
• • •
▪ cause decay
Bacteria stick to food and cause decay.
▪ prevent decay
You can use a preservative on the wood to prevent further decay.
■ ADJECTIVES/NOUN + decay
▪ tooth/dental decay
Eating too much sugar causes tooth decay.
▪ natural decay
Everything in our environment is subject to natural decay.
▪ the process of decay
The natural processes of decay gradually destroys archaeological sites.
▪ a sign of decay
I couldn't see any signs of decay on the fruit.