Where Derrida writes that “différance is literally neither a word nor a concept” he is of course being highly obscure about what he means. He is hoping that the reader is aware of the atomistic understanding of language whereby a word, as its most literal, is an isolated cup of meaning from which one can drink indefinitely without loss of volume or flavour. It is this understanding that Derrida is calling into question, among other things, replacing it in his eyes with the understanding that all words are contaminated by the meanings of other words, that words quite literally defer their meanings onto other words because they need to differ themselves from other words. Hence the play on ‘différer’ which means both ‘to differ’ and ‘to defer’.
This contamination is for Derrida not only inescapable but actually necessary for the differential network of language to be possible, for “the principle, first enounced by Saussure, that language is a differential network of meaning. There is no self-evident or one-to-one link between signifier and signified… both are caught up in a play of distinctive features where differences of sound sense are the only markers of meaning.” (Norris, Deconstruction, 1982) However Derrida takes a few steps beyond Saussure’s ‘differential network’ by placing différance on the fringe (neither in nor out) of the differential network, différance being the condition of possibility of difference. Or, "Better, the play of difference, which, as Saussure reminded us, is the condition for the possibility and functioning of every sign, is in itself a silent play."
He continues, "What am I to do in order to speak of the a of différance? It goes without saying that it cannot be exposed. One can expose only that which at a certain moment can become present, manifest, that which can be shown, presented as something present, a being-present in its truth, in the truth of a present or the presence of the present. Now if différance is (and I also cross out the ‘is’) what makes possible the presentation of the being-present, it is never presented as such. It is never offered to the present. Or to anyone."
Derrida is also using the word différance as an example of the theory which I’ve briefly outlined, of all words being present not only to their intended meanings but also to any number of other possible meanings, "Thus the word différance (with an a) is to compensate economically - this loss of meaning, for différance can refer simultaneously to the entire configuration of its meanings. It is immediately and irreducibly polysemic, which will not be indifferent to the economy of my discourse here. In its polysemia this word, of course, like any meaning must defer to the discourse in which it occurs, its interpretive context; but in a way it defies deriving from the present participle (differant), thereby bringing us close to the very action of the verb differer, before it has even produced an effect constituted as something different or as difference"
Hence différance is literally not a word inasmuch as it is several words simultaneously (not solely by virtue of being a pun) and is not a concept in that there is no stable entity signified by the sound/image ‘différance’.
Coming soon: the signifier as secondary and provisional to the signified and the upsetting of this opposition.