This is one of the better definitions of myth that I’ve seen. It’s from an essay entitled, Story, Myth, Dream & Drama.

What is myth then? Myths are stories, but not just any stories. They are stories of special symbolic significance. Myths are prototypical stories, concretising the really fundamental themes of human existence; involving archetypal characters and situations; expressing the really basic curiosities, hopes, fears, desires, conflicts, choices and patterns of resolution. Myths are paradigmatic stories, ie, stories that are told and retold as shedding light on other stories, as linking past and present, as bringing the unknown into relation with known. Myths are resonating narratives, embodying the distilled essence of human experience; giving symbolic answers to the most basic human questions, questions of origin and destiny; offering stylised solutions to the most basic human decisions; staking out the choices to be made at life’s cross-roads. Myths are normative narratives, setting out a society’s history, legitimating its institutions, codes and values and envisioning its future development. Myths are synthesising stories, capturing the zeitgeist of a time and place, bringing to a focus what forces are at work, highlighting its problems, and crystallising its values.