decay

The word “decay” means to rot or gradually break down, especially of organic matter. In plain terms, to rot or gradually get worse — used for teeth, buildings, empires, and even radioactive atoms.

“Decay” is pronounced dih-KAY (/diˈkeɪ/ in IPA).

Here is “decay” used in a sentence: “The fallen leaves slowly decayed into the soil.”

Words with a similar meaning to “decay” include fester.

Depending on how it is used, “decay” can be a verb and a noun.

The word “decay” comes from Latin. From Anglo-Norman decaeir, ultimately from Latin dē- ("down, away") + cadere ("to fall") — the same root as "decadent" and "decadence.".

“Decay” is a fairly common word in modern English, usually learned at around the B2 level.

“Decay” has 4 distinct senses listed in this dictionary. The most common is: to rot or gradually break down, especially of organic matter.

Decay is the broader term, covering both the gradual breakdown of organic matter and the decline of quality, strength, or condition in non-organic things like buildings or institutions. Rot specifically refers to organic decomposition and is essentially one type of decay.

In physics, decay describes the process by which an unstable atomic nucleus or particle breaks down over time, releasing energy or particles as it transforms into a more stable state. This is a specialized, technical use distinct from decay's everyday meaning of rotting or declining.

Yes, decay is commonly used figuratively to describe the gradual decline in quality, strength, or condition of abstract things, such as moral decay or the decay of a relationship, not just physical or organic breakdown.