The Deep Syntactic Structure (DSyntS) is a dependency tree whose nodes are labeled with deep lexical units (DLUs) of the language in question and the branches with the names of the universal deep syntactic relations (DSyntRels).

All deep syntactic relations relations are claimed to be universal in the sense that they are necessary and sufficient:

• For each given deep syntactic relations //R//, it is possible to find several syntactic constructions in some language such that you need //R// to describe the construction at the DSynt-level.
• It is claimed that there is no widespread syntactic construction in a reasonable number of languages that cannot be described using this set of DSynt-relations.

There exist, however, rather exceptional syntactic constructions actually carrying a lexical meaning. For those, MTT introduces fictitious lexemes : A fictious lexeme expresses, in a DSyntS, the lexical meaning carried by such a syntactic construction.