[[Lacan]] defines the [[sign]] as that which "represents something for someone," in opposition to the [[signifier]], which is "that which represents a subject for another signifier."<ref>{{S11}} p. 207</ref>
=====Semotics=====
By engaging with the concept of the [[sign]], [[Lacan]] sets his work in close relation to the [[science]] of [[semiotics]], which has grown rapidly in the twentieth century.
Two main lines of development can be discerned within [[semiotics]]: the European line associated with [[Ferdinand de Saussure]] (which [[Saussure]] himself baptized with the name of "[[semiology]]"), and the North American line associated with [[Charles S. Peirce]].
===Ferdinand de Saussure===
For [[Lacan]], this [[algorithm]] defines "the [[topography]] of the [[unconscious]]."<ref>{{E}} p.163</ref>
===Charles S. Peirce===
According to [[Peirce]], the [[sign]] is something whcih represents an [[object]] to some interpretant (the term "object can mean, for [[Peirce]], a physical thing, an event, an idea, or another [[sign]]).
[[Peirce]] divides [[signs]] into three classes: "[[symbol]]s", "[[index|indices]]" and "[[icon]]s," which differ in the way they relate to the [[object]].
The [[symbol]] has no "natural" or necessary relationship to the [[object]] it refers to, but is related to the [[object]] by a purely conventional rule.
The [[index]] has an "existential relation" to the [[object]] it represents (i.e. the [[index]] is always spatially or temporally contiguous to the [[object]]).
The [[icon]] represents an [[object]] by exhibiting its form via similarity.
[[Peirce]]'s distinctions between [[icon]]s, [[index|indices]] and [[symbol]]s are analytical and not intended to be mutually exclusive.
Hence a [[sign]] will almost always function in a variety of modes; personal pronouns, for example, are [[sign]]s which function both symbolically and indexically.
=====Jacques Lacan=====
[[Lacan]] takes up [[Peirce]]'s concept of the [[index]] in order to distinguish between the [[psychoanalytic]] and medical concepts of the [[symptom]], and to distinguish between (animal) [[code]]s and (human) [[language]]s.
[[Lacan]] also develops the concept of the [[index]] along the lines set down by [[Roman Jakobson]] in the concept of the [[shifter]], to distinguish between the [[subject]] of the [[statement]] and the [[subject]] of the [[enunciation]].
