Myth – “A traditional story…which embodies and provides an explanation, aetiology, or justification for something…” In this case, a cultural conviction; an archetype.
Mytheme – after Lacan’s matheme; a symbolic representation of ideas and analyses. In this case, the archetype or myth expressed in culture.
Thematic – “The subject of discourse, discussion, conversation, meditation, or composition; a topic.”
Mathematics – “Originally: (a collective term for) geometry, arithmetic, and certain physical sciences involving geometrical reasoning, such as astronomy and optics; spec. the disciplines of the quadrivium collectively. In later use: the science of space, number, quantity, and arrangement, whose methods involve logical reasoning and usually the use of symbolic notation, and which includes geometry, arithmetic, algebra, and analysis; mathematical operations or calculations.”
[Quoted definitions are taken from Oxford English Dictionary Online.]