myth

Concise Oxford English Dictionary © 2008 Oxford University Press:
myth/mɪθ/

▶noun

• 1 a traditional story concerning the early history of a people or explaining a natural or social phenomenon, and typically involving supernatural beings or events.

• 2 a widely held but false belief.

  ■ a fictitious person or thing.

  ■ an exaggerated or idealized conception of a person or thing.

– derivatives
mythic adjective,
mythical adjective,
mythically adverb.

– origin C19 (earlier (C17) as mythic): from mod. L. mythus, via late L. from Gk muthos.