myth

Etymology

From Ancient Greek μῦθος (mûthos, “word, humour, companion, speech, account, rumour, fable”). Attested in English since 1830. Doublet of mythos.

noun

1. A traditional story which embodies a belief regarding some fact or phenomenon of experience, and in which often the forces of nature and of the soul are personified; a sacred narrative regarding a god, a hero, the origin of the world or of a people, etc.
   Jacobsen's theory about the empty storehouse is still valid, for a myth never has one meaning only; a myth is a polyphonic fugue of many voices. 1981, William Irwin Thompson, The Time Falling Bodies Take to Light: Mythology, Sexuality and the Origins of Culture, London: Rider/Hutchinson & Co., page 175
2. (uncountable) Such stories as a genre.
   Myth was the product of man's emotion and imagination, acted upon by his surroundings. (E. Clodd, Myths & Dreams (1885), 7, cited after OED)
3. A commonly-held but false belief, a common misconception; a fictitious or imaginary person or thing; a popular conception about a real person or event which exaggerates or idealizes reality.
   Scientists debunk the myth that gum stays in the human stomach for seven years.
4. A person or thing held in excessive or quasi-religious awe or admiration based on popular legend
   Father Flanagan was legendary, his institution an American myth. (Tucson (Arizona) Citizen, 20 September 1979, 5A/3, cited after OED)
5. A person or thing existing only in imagination, or whose actual existence is not verifiable.
   As for Mrs. Primmins's bones, they had been myths these twenty years. 1849, Edward Bulwer-Lytton, The Caxtons
   Living beyond the Omega-4 mass relay in the Terminus Systems, the mysterious Collector species is glimpsed so rarely as to be taken for a myth by most in galactic society. In reality, Collectors are human-sized insectoid bipeds and can resemble massive winged beetles. They are a terrifying force in the galaxy, responsible for the murder of hundreds of thousands. 2010, BioWare, Mass Effect 2 (Science Fiction), Redwood City: Electronic Arts, →OCLC, PC, scene: Collectors Codex entry
6. An invented story, theory, or concept.
   His story is a pure myth.