What 'is' deconstruction? (The use of the quotation marks should make clear that the question cannot in fact be posed like this. cf. Deconstruction: Between Method and Singularity.) A first option for a description of deconstruction is offered by the dictionary. In the French dictionary, Littré, the meaning of deconstruction progresses along two lines. (1) Grammatical. Deconstruction means change, the disruption of the construction or the composition of the words in a sentence with the purpose of producing other, new meanings with the same words (i.e., not to deny them!). (2) Mechanical. Deconstruction indicates disassembling, taking apart, dismantling, disintegrating (Derrida often uses the word 'demontage').
 In the most simple and general terms, deconstruction in the Derridean sense means to read a text according to a certain way or strategy, a precise and careful strategy, but also one that shakes the ground under one's feet. It is a praxis in which Derrida specifically aims to transform philosophical, linguistic, theological, or aesthetic texts. Deconstruction shows us the possibility of continually ascribing different or additional meanings to texts; it acknowledges the fundamental ambiguity of signs and texts and the impossibility of controlling them. Deconstruction implies transplantation, the ability to remove a sign or text from its present context to another context. In this way, deconstruction highlights the heterogeneity of a sign or a text. It wants to show the impossibility of a (sign-)system to close, to arrive at a definite meaning. Of course, attempts to demarcate meanings take place all the time, but the demarcations are based on conventions and are always tentative ('for the time being').
 Deconstruction disrupts a text from the inside out. This means that deconstruction operates from within a text, from within the vocabulary of the text that it deconstructs. It necessarily operates from the inside, borrowing all the strategic and economic resources of the subversions from the old structure, borrowing them structurally (cf. Of Grammatology, p.24). Derrida shows that every text is always permeated by multiple meanings. But this heteronomy is relegated to the background by the author, by a reader or by the context in such a way as to favor one meaning over another. Such manifestation of power is revealed and questioned in deconstruction. For that reason, deconstruction is not a discursive or theoretical 'play', but a practical-political affair; it is the taking of responsibility (cf. Music, Deconstruction, and Ethics) .
 Derrida emphasizes the affirmative character of deconstruction, the ethics of deconstruction. 'Deconstruction is not an enclosure in nothingness (a sort of gratuitous chess game), but an openness towards the other ... an otherness that has been dissimulated or appropriated by the logocentric tradition ... The very activity of thinking, which lies at the basis of epistemological, ontological, and veridical comprehension, is the reduction of plurality to unity and alterity to sameness ... To think philosophically is to comprehend, to include, to seize, to grasp and master the other, thereby reducing its alterity. Deconstruction may therefore be understood as the desire to keep open a dimension of alterity which can neither be reduced, comprehended, nor, strictly speaking, even thought by philosophy' (Kearney, p.123-4, my italics). The crucial 'methodological' point is that it is possible to discern the operations of different ways of meaning simultaneously. To think in multiplicity. Derrida's argument is that the unconditional arises as the interruption, or non-closure, of any determinate context.
 According to Simon Critchley, the principle of alterity within a deconstructive praxis can be found in the strategy of 'double reading'. 'If the first moment of reading is the rigorous, scholarly reconstruction of the dominant interpretation of a text, its intended meaning (vouloir-dire) in the guise of a commentary, then the second moment of reading, in virtue of which deconstruction obeys a double necessity, is the destabilization of the stability of the dominant interpretation' (Critchley, p.26). The second moment contradicts the text with itself, opening its intended meaning to an alterity that goes against what a text was purported to say or mean. (An example of a double reading in music can be found in Gerd Zacher's Kunst einer Fuge [Art of a Fugue].) Derrida often articulates this double reading around what is called undecidables.