The state or quality of being decayed; the condition of having undergone decomposition or deterioration.
From decayed + -ness (state or quality). Decayed comes from decay (from Old French and Latin) + -ed (past participle), making -ness convert the adjective to an abstract noun.
The 'decayedness' of a log in the forest creates one of nature's most diverse ecosystems—decomposing wood feeds countless insects, fungi, and microorganisms.
Complete word intelligence in one call. Free tier — 50 lookups/day.