It is in La relation d'objet that Lacan introduces the algebraic symbol for the barred Other, and lack comes to designate the lack of the signifier in the Other. Then the relation of the subject to the lack of the signifier in the Other, designates the signifier of a lack in the Other. No matter how many signifiers one adds to the signifying chain, the chain is always incomplete, it always lacks the signifier that could complete it.