myth

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.

2. 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.”