Terms often used in discussing myths:

aetiological  Aetiology is the study of causes, origins, reasons.  In mythology, an aetiological myth explains, superficially at least, the reasons why a certain state affairs exists.  For example, Hesiod states that the story of Prometheus trying to trick Zeus by offering him only bones concealed in fat "explains" why humans offer sacrifices of bones to the gods.  [Greek, aition, cause + logos, word, the study of.]

apotropaic warding off or "turning away" evil.  [Greek apo an intensifier + tropos a turn.]

autochthonous native to a particular place; aboriginal; indigenous.  Sometimes these original inhabitants were thought to have been born directly from the earth.  See chthonic.

cosmogony The study of or a theory of the creation and evolution of the universe.  Sometimes creation myths are termed cosmogonies. [Greek cosmos, order, the universe, the world + gonos, creation, birth.]

cosmology Similar to cosmogony above, but with less emphasis on creation or origins and more on the study of how the universe works now.  These two terms are both used in modern astrophysics.

chthonic (pronounced "thon'-ic") Pertaining to gods and spirits of the underworld.  [Greek, khthonios, under the earth, khthon, the earth.]

ennead Any group or set of nine.  In Egyptian mythology, this term is applied to the nine most important gods, as codified by the priests of Heliopolis ("Sun City").  [Greek, enneas, nine.]

eponymous Giving one's name to something, as to a city, country, era, institution.  [Greek, epi to + onoma, name]

etymology The study of word origins and derivation.  In mythology, scholars often use etymology to bolster their arguments.  Sometimes these etymologies are uncertain or mistaken, however.  I have found three different explanations of the word "Titans:"  1. "lord" (Graves), 2. "white clay-men" (Harrison), and 3. "day," "sun" (Am. Heritage Dictionary).

mythology Literally, the study of myths. [Greek, muthos, utterance, story, plot + logos word, reason, the study of.]

theogony A recitation of the origin and genealogy of the gods, especially as in ancient epic poetry.  [Greek, theos, god + gonos, creation, birth.]  This is different from theology, the rational inquiry into religious questions.

theriomorphic In the form of a beast.  [Greek, therion, wild beast + morph, form].