American Heritage Dictionary Entry: decay HOW TO USE THE DICTIONARY To look up an entry in The American Heritage Dictionary of the English Language, use the search window above. For best results, after typing in the word, click on the “Search” button instead of using the “enter” key. Some compound words (like bus rapid transit, dog whistle, or identity theft) don’t appear on the drop-down list when you type them in the search bar. For best results with compound words, place a quotation mark before the compound word in the search window. guide to the dictionary THE USAGE PANEL The Usage Panel is a group of nearly 200 prominent scholars, creative writers, journalists, diplomats, and others in occupations requiring mastery of language. Annual surveys have gauged the acceptability of particular usages and grammatical constructions. The Panelists NEED HELP SOLVING A CROSSWORD PUZZLE? Go to our Crossword Puzzle Solver and type in the letters that you know, and the Solver will produce a list of possible solutions. -- AMERICAN HERITAGE DICTIONARY APP The new American Heritage Dictionary app is now available for iOS and Android. THE AMERICAN HERITAGE DICTIONARY BLOG The articles in our blog examine new words, revised definitions, interesting images from the fifth edition, discussions of usage, and more. OPEN DICTIONARY PROJECT Share your ideas for new words and new meanings of old words! Start Sharing Now! -- See word lists from the best-selling 100 Words Series! Find out more! INTERESTED IN DICTIONARIES? Check out the Dictionary Society of North America at http://www.dictionarysociety.com de·cay (dĭ-kā) Share: Tweet v. de·cayed, de·cay·ing, de·cays v.intr. 1. Biology To break down into component parts; rot. 2. Physics To disintegrate in a process of radioactive decay or particle decay. 3. Electronics To decrease gradually in magnitude. Used of voltage or current. 4. Aerospace To decrease in orbit. Used of an artificial satellite. 5. To fall into ruin: a civilization that had begun to decay. 6. To decline in health or vigor; waste away. 7. To decline from a state of normality, excellence, or prosperity; deteriorate. v.tr. To cause to decay. n. 1. a. The destruction or decomposition of organic matter as a result of bacterial or fungal action; rot. b. Rotted matter. 2. Physics a. See radioactive decay. b. See particle decay. 3. Aerospace The decrease in orbital altitude of an artificial satellite as a result of conditions such as atmospheric drag. 4. A gradual deterioration to an inferior state: tooth decay; urban decay. 5. A falling into ruin. [Middle English decayen, from Old French decair, from Vulgar Latin *dēcadere : Latin dē-, de- + Latin cadere, to fall; see kad- in the Appendix of Indo-European roots.] de·cayer n. Synonyms: decay, rot, decompose, putrefy, spoil, molder, disintegrate These verbs refer to the gradual process by which something breaks down or falls apart as a result of natural causes. Decay has wide application but often suggests partial deterioration short of complete destruction: "A decaying dam is an accident waiting to happen" (George Black). Rot and decompose are closely synonymous with decay, but rot often emphasizes loss of structural integrity while decompose generally stresses breaking down into chemical components: The rotting timbers gave way under the added weight. When grass clippings decompose, they return nutrients to the soil. Putrefy denotes an advanced stage of organic breakdown that is offensive to the senses: "Large numbers of cows and oxen ... were left to putrefy on mud flats after the floods receded, attracting rats" (John F. Burns). Spoil usually refers to the process by which perishable substances become unfit for use or consumption: Fish will spoil quickly if not refrigerated. To molder is to crumble to dust: The shawl had moldered away in the trunk. Disintegrate refers to the reduction of something to particles, fragments, or constituent elements: The sandstone façade had disintegrated from exposure to wind and rain. The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved. Indo-European & Semitic Roots Appendices Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices: Indo-European Roots Semitic Roots The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots. 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