The Differential Relationship Between Signifier and Subject

Lacan's emphasis is on a differential system of language and that carries through to his theory of repetition. Repetition for Lacan is always repetition with a difference, Kierkegaard figured this out long time ago. It's the bar between S1 and S. That's little A allows us to talk about this third element that is the differential relationship here between the signifier and the subject it represents. How in the fuck does this relate to repetition? That's the question.