Linguistic constructs often correspond to nothing concrete: Descriptivists’ zero morpheme, generativists’ trace, variationists’ null instantiation, and Columbia School’s null signal. These represent structural relations with no phonetic substance. Columbia School has posited, moreover, three types of relatively insubstantial semantic structure: The residual member and the including member are semantic value oppositions within a grammatical system, each defined by the system’s other members. In the opposition of substance, in my own work, two signals share a value from one semantic substance but only one of them bears a meaning from an additional semantic substance. All of these constructs are justified by distributional facts within theoretical paradigms. It is possible, too, to distinguish between all of the above and absence.
Davis, Joseph C. M., "Spooky Grammatical Effects" (2018). CUNY Academic Works.