decomposition

Decomposition (or spoilage) refers to the reduction of the body of a formerly living organism into simpler forms of matter.
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n. decomposition, breaking down, mouldiness, moldiness, taint

(n.)
The state of being reduced into original elements.
  

(n.)
The act or process of resolving the constituent parts of a compound body or substance into its elementary parts; separation into constituent part; analysis; the decay or dissolution consequent on the removal or alteration of some of the ingredients of a compound; disintegration; as, the decomposition of wood, rocks, etc.
  

(n.)
Repeated composition; a combination of compounds.
  

The breakdown of matter by bacteria and fungi, changing the chemical makeup and physical appearance of materials.