What's the difference between a myth and a legend?

In folkloric nomenclature, a myth takes place before or at the creation of the world, and it's characters usually are not human - or at best, they have "superhuman" characteristics. A legend takes place after the creation of the world and its characters are usually human. Legends are further divided into memorates and fabulates - and, rather confusingly "legends" (my quotes). A memorate is grounded closely to present reality and those still living; most "urban legends" are memorates. A fabulate is more detatched from reality, often with fantastic elements included. Technically, as a fabulate grows more detatched from everyday reality, it develops into a "legend" - e.g., "The Labors of Hercules" and "Theseus and the Minotaur" are legends. Both myths and legends are traditionally considered true by the cultures that tell them - as opposed to the third major class of narrative folklore, the folktale, which is acknowledged to be fictional.

http://links.jstor.org/sici?sici=0043-373X(199010)49%3A4%3C371%3A%22HNTFF%3E2.0.CO%3B2-K

You may not have access to this article, but it is widely available in most university libraries, and the above definitions are really very standard in the discipline and can be found in a number of references.

Also note that "truth" is not a distinguishing characteristic in myths or legends. "The Unsolvable Math Problem" is (mostly) a true story, but it's detatchement from specific characteristics and oral character makes it a legend. Genesis through the Noah story is properly categorized as a myth, even if it is true.

In his article, "The Forms of Folklore: Prose Narratives," William Bascom gives the following definitions of myth and legend:

Myths are considered true sacred stories that occurred in the remote past and have non-humans (gods, monsters) as the principal characters.

Legends are considered true stories primarily about human heroes that occurred in the recent past and may feature some religious references. Example: Odyssey.


http://faculty.gvsu.edu/websterm/MythFAQs.htm

There is very little difference between the two, except that a myth is traditionally tied to a moral or an explanation of a natural event. A legend does not necessarily need a reason. An example would be the myth of the Tower of Babel which explains why we have different languages, compared to the legend of big foot whose existence or lack thereof means very little.

http://www.merriam-webster.com/dictionary/legend
http://www.merriam-webster.com/dictionary/myth

Some of the things myths explain are the traditions, morals, and customs of an ancient culture. They also explain the creation of the universe, world, people, and animals. Supernatural beings figure heavily in myths.

Legends are traditional folklore passed down generationally in oral storytelling that is historically based but embellished with details of mankind being helped by the supernatural at times. An example would be the Gods of Mount Olympus helping the warriors during the Trojan war. The city of Troy has been found. But definite proff of the Greek Gods has not been found.

A *fable* is a short moral story. The characters are anthropomorphized animals.


myth (m?th)
n.
1.a. A traditional, typically ancient story dealing with supernatural beings, ancestors, or heroes that serves as a fundamental type in the worldview of a people, as by explaining aspects of the natural world or delineating the psychology, customs, or ideals of society: the myth of Eros and Psyche; a creation myth.


leg·end (l?j??nd)
n.
1.a. An unverified story handed down from earlier times, especially one popularly believed to be historical.
1. a popular story handed down from earlier times whose truth has not been ascertained
2. a group of such stories: the Arthurian legend.


fable

fa·ble (f??b?l)
n.
1. A usually short narrative making an edifying or cautionary point and often employing as characters animals that speak and act like humans.
n
1. (Literary & Literary Critical Terms) a short moral story, esp one with animals as characters

http://www.thefreedictionary.com/Myth
http://www.thefreedictionary.com/Legend
http://www.thefreedictionary.com/fable