*SET-U

English word origin

Etymology of decay

From Middle English decaien (“to decrease, diminish”) and decai (“deterioration, decline in value”), from Anglo-Norman decaeir (“to fall away, decay, decline”), from Vulgar Latin *dēcadere, etymologically restored form o

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In this entry · 1 source sections

The source etymologies

Wiktionary via Kaikki / Wiktextract

The source reports below are imported and unreviewed by *SET-U. Separate numbered origins and differing source variants are preserved; agreement within this extraction is not independent corroboration.

Unnumbered source etymology

Original entry ↗
noun

Rot; any processes or result of organic matter being gradually decomposed, especially by microbial action. · Deterioration of condition; loss of status, quality, strength, or fortune. · Radioactive decay; decomposition of an atom or its nucleus. · Particle decay; decomposition of a sub-atomic particle.

verb

To deteriorate, to get worse, to lose strength or health, to decline in quality. · To undergo bit rot, that is, gradual degradation. · To undergo software rot, that is, to fail to be updated in a changing environment, so as to eventually become legacy or obsolete. · To undergo prolonged reduction in altitude (above the orbited body).

Selected source glosses provide context, not a complete modern definition inventory

From Middle English decaien (“to decrease, diminish”) and decai (“deterioration, decline in value”), from Anglo-Norman decaeir (“to fall away, decay, decline”), from Vulgar Latin *dēcadere, etymologically restored form of Latin dēcidere (“to fall down, to fail, sink or perish”), from de- (“of, from, away, down”) + cadere (“to fall”). Compare decadent and decadence.

Relationships mentioned by the source

These are extracted mentions, not a timeline or a verified sequence of immediate parents.

  • Root classification mention*ḱh₂d-ine-pro
  • Inherited-form mentiondecaienenm
  • Derivation mentiondēcidōla · to fall down, to fail, sink or perish

This page abbreviates 9 auxiliary source items. The etymology narrative is not shortened. Omission counts are available in the audit fields below; consult the original for complete auxiliary material.

Inspect preserved source fields

Raw extraction fields are retained for auditing. Their order does not establish ancestry.

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    {
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      "args": {
        "1": "en",
        "2": "ine-pro",
        "3": "*ḱh₂d-"
      },
      "expansion": ""
    },
    {
      "name": "inh",
      "args": {
        "1": "en",
        "2": "enm",
        "3": "decaien",
        "4": "",
        "5": "to decrease, diminish"
      },
      "expansion": "Middle English decaien (“to decrease, diminish”)"
    },
    {
      "name": "der",
      "args": {
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        "2": "xno",
        "3": "decheoir",
        "4": "decaeir",
        "t": "to fall away, decay, decline"
      },
      "expansion": "Anglo-Norman decaeir (“to fall away, decay, decline”)"
    },
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      "expansion": "Vulgar Latin *dēcadere"
    },
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        "4": "dēcidere",
        "t": "to fall down, to fail, sink or perish"
      },
      "expansion": "Latin dēcidere (“to fall down, to fail, sink or perish”)"
    }
  ],
  "links": [
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      "decaien",
      "decaien#Middle_English"
    ],
    [
      "decai",
      "decai#Middle_English"
    ],
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      "decaeir",
      "decheoir#Old_French"
    ],
    [
      "dēcidere",
      "decido#Latin"
    ],
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      "de-",
      "de-#Latin"
    ],
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      "cadere",
      "cado#Latin"
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    ],
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      "decadence#English"
    ]
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  "descendants": [],
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        "Rot; any processes or result of organic matter being gradually decomposed, especially by microbial action.",
        "Deterioration of condition; loss of status, quality, strength, or fortune.",
        "Radioactive decay; decomposition of an atom or its nucleus.",
        "Particle decay; decomposition of a sub-atomic particle."
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      "pos": "verb",
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        "To deteriorate, to get worse, to lose strength or health, to decline in quality.",
        "To undergo bit rot, that is, gradual degradation.",
        "To undergo software rot, that is, to fail to be updated in a changing environment, so as to eventually become legacy or obsolete.",
        "To undergo prolonged reduction in altitude (above the orbited body)."
      ],
      "tags": [
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}

Where this record stops

This page does not supply an independently verified sound-change sequence, first-use manuscript or complete family tree unless a cited analysis explicitly establishes one. Missing detail here is a limit of this record—not a claim that humanity knows nothing more.

An older meaning does not determine what a word must mean today. Follow the sources, preserve disagreements, and keep ancestry separate from interpretation.

Contribute located evidence for decay →

Source and snapshot

Imported from Wiktionary contributors; extracted by Tatu Ylonen / Wiktextract / Kaikki.org. Selected fields are reformatted and grouped; wording, source identity and etymology sections are retained. CC-BY-SA-4.0 applies to the imported source material.

Dump: 2026-10-01 · Extracted: 2026-10-30. These are snapshot dates, not the word’s first attestation or the page’s revision date.

Source entry and bibliography ↗Wiktionary revision history ↗Acquisition and rights ledger
Machine-source provenance
Source SHA-256
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Import run
73216b9a9b78ed3830994bf853103716f5a4dc57099e371e9f8fdc468facca26
Permanent entry ID
w-ZGVjYXk