英：lack; 法：manque
在拉康的教学之中，“缺失”这一术语始终联系着欲望（DESRE)。正是某种缺失导致了欲望的升腾 (见：S8,139)。然而，缺失之物的确切性质随着拉康的著述过程而有所改变。
当该术语在1955年首度出现的时候，缺失首先指代的是存在 (BENG)的缺失（这里与萨特存在着一些紧密的对应关系；见：Sartre, 1943)。被欲望之物即存在 (being)本身。“欲望即存在与缺失之间的关系。严格地讲，缺失即存在之缺失。它不是这个抑或那个的缺失，而是存在之缺失，存在 (being)正是借由此种存在之缺失而得以实存 (exist)的”(S2,223)。拉康在1958年又返回了这一主题，他在此时宣称欲望即存在之缺失 (法：manqueàetre; 谢里丹将其译作“存在之想望”[want-to-be], 施耐德曼则将其译作“存在之匮乏”[want of being])的换喻 (见：E, 259)。主体的存在之缺失即“分析经验的核心”，也是“神经症患者的激情在其中得以展开的真正领域”(E, 251)。拉康把“存在之缺失”与“拥有之缺失”(manqueàavoir)对立了起来，前者联系着欲望，后者则联系着要求 (Ec, 730)。
| 动因 | 缺失 | 对象 |
|---|---|---|
| 实在的父亲 | 象征的阉割 | 想象的阳具 |
| 象征的母亲 | 想象的挫折 | 实在的乳房 |
| 想象的父亲 | 实在的剥夺 | 象征的阳具 |
| 三类对象缺失表 |
在1956年，缺失开始指代某种对象的缺失。根据所缺失的对象的性质，拉康区分了三种类型的缺失，如表2所示（取自：S4,269).
从分析经验的视角来看，阉割在此三种形式的缺失中是最为重要的一种，而且“缺失”这一术语也倾向于变成阉割的同义词 (见：阉割情结[CASTRATION COMPLEX]).
在1957年，当拉康引入被画杠的大他者 (A)的代数学符号时，缺失便开始指代大他者中的一个能指的缺失。拉康引入了符号S (A)来表示“大他者中缺失的能指”。无论我们给能指链条增添多少能指，能指链条都总是不完整的；它总是缺失那个能够将其补全的能指。这个“佚失的能指”(missing signifier,. 在拉康的代数学中写作：-1)构成了主体。
(mangue) The term 'lack'is always related, in Lacan's teaching, to DESIRE. It is a lackwhich causes desire to arise (see S8,139). However, the precise nature of what is lackingvaries over the course of Lacan's work.
When the term first appears, in 1955, lack designates first and foremost a lack ofBEING (there are close parallels with Sartre here; see Sartre, 1943). What is desired isbeing itself. Desire is a relation of being to lack. The lack is the lack of being properlyspeaking. It isn't the lack of this or that, but lack of being whereby the being exists' (S2,223). Lacan returns to this theme in 1958, when he argues that desire is the metonymy ofthe lack of being (manque a etre; translated by Sheridan as 'want-to-be'and by Schneiderman as 'want of being'; see E, 259). The subject's lack of being is 'the heart ofthe analytic experience'and 'the very field in which the neurotic's passion is deployed' (E, 251). Lacan contrasts the lack of being, which relates to desire, with the lack ofhaving (mangue a avoir), which relates to demand (Ec, 730)
In 1956, lack comes to designate the lack of an object. Lacan distinguishes between threekinds of lack, according to the nature of the object which is lacking, as shown in Figure 7 (taken from S4,269).
Of these three forms of lack, castration is the most important from the point of view ofanalytic experience, and the term'lack'tends to become synonymous with castration (see CASTRATION COMPLEX).
In 1957, when Lacan introduces the algebraic symbol for the barred Other （A）. Lack comes to designate the lack of a signifier in the Other. Lacan introduces the symbol S(A)to designatethe 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 thesignifier that could complete it.This 'missing signifier'(written-1 in Lacanian algebra)is constitutive of the subject.