Difference is a key concept of philosophy, denoting the process or set of properties by which one entity is distinguished from another within a relational field or a given conceptual system.
Leibnitz [sic] regarded phaenomena as things in themselves, consequently as intelligibilia, that is, objects of pure understanding ..., and in this case his principle of the indiscernible (principium identatis indiscernibilium) is not to be impugned.
This concept first came to prominence in the structuralist writings of Swiss linguist Ferdinand de Saussure and was developed for the analysis of social and mental structures by French anthropologist Claude Lévi-Strauss.
The former was concerned to question the prevailing view of meaning "inhering" in words, or the idea that language is a nomenclature bearing a one-to-one correspondence to the real.
[3][4] The French philosopher Jacques Derrida both extended and profoundly critiqued structuralist thought on the processes by which meaning is produced through the interplay of difference in language, and in particular, writing.
[7] Elsewhere, Derrida coined the term différance (a deliberate misspelling of différence) in order to provide a conceptual hook for his thinking on the meaning processes at work within writing/language.
The "phonemic" (non-)difference between différence and différance can only be observed in writing, hence producing differential meaning only in a partial, deferred and entangled manner.