The Concept of the Sign
The term "bar" first appears in Lacan's work in 1957, where it is introduced in the context of a discussion of Ferdinand de Saussure's concept of the sign.<ref>Lacan, Jacques. Écrits: A Selection. Trans. Alan Sheridan. London: Tavistock Publications, 1977. p.149</ref>In this context, the bar is the line that separates the signifier from the signified (in the Saussurean algorithm), and stands for the resistance inherent in signification which is only crossed in metaphor.
The Barred Subject
Not long after the 1957 paper in which the term first appears, in the seminar of 1957-8, Lacan goes on to use the bar to strike through his algebraic symbols S and A in a manner reminiscent of Heidegger's practice of crossing out the word "being."<ref>Heidegger, Martin. (1956) The Question of Being, trans. William Kluback and Jean T. WIlde, London: Vision, 1959.</ref>The bar is used to strike through the S to produce, , the "barred subject'." The bar here represents the division of the subject by language, the split. Thus whereas before 1957 S designates the subject (e.g. in schema L), from 1957 on S designates the signifier and designates the (divided) subject.
The Barred Other
The bar is also used to strike through the A (the big Other) to produce the algebraic notation for the "barred Other,"
A. However, Lacan continues to use both signs in his algebra (e.g. in the graph of desire). The barred Other is the Other insofar as it is castrated, incomplete, marked by a lack, as opposed to the complete, consistent, uncastrated Other, an un-barred A, which does not exist.
"Woman Does Not Exist"
In 1973 the bar is used to strike through the definite article la whenever it precedes the noun femme ("woman"), as in Lacan's famous phrase la femme n'existe pas ("woman does not exist"). The definite article in French indicates universality, and by crossing it out Lacan illustrates his thesis that femininity is resistant to all forms of generalisation.<ref>Lacan, Jacques. Le Séminaire. Livre XX. Encore, 1972-73. Ed. Jacques-Alain Miller. Paris: Seuil, 1975. p.68</ref>
In addition to these functions, the bar can also be interpreted as the symbolic phallus (which itself is never barred), as the symbol of negation in the formulae of sexuation (see sexual difference), and as the trait unaire (see identification).