decay
de-cay
verb
To rot or decompose gradually through natural processes, often due to neglect.
"The old wooden fence began to decay."
noun
The state or process of rotting or gradual deterioration from a sound condition.
"We observed the decay in the ancient ruins."
Thesaurus
Synonyms: radioactive decay, disintegration, crumble, dilapidate, decomposition, disintegrate, decompose, decline