What the logical analysis does is to bring out the recursive aspect of the modifying relation, showing the nominal group as a regressive bracketing. This is the property that generates long strings of nouns such as are found in headlines and the names of parts of machines [...] We refer to this as UNIVARIATE structure, a structure generated by the recurrence of the same function [...] The type of structure exemplified by Deictic + Numerative + Epithet + Classifier + Thing + Qualifier we call a MULTIVARIATE structure: a constellation of element each having a distinctive function with respect to the whole.
- Halliday (1985), Pag. 172

Parataxis and hypotaxis define a kind of structure that we have called ʻunivariateʼ, to distinguish it from the multivariate structures that we find everywhere else. A multivariate structure is a configuration of different functional relationships, like Theme – Rheme, or Actor – Process – Beneficiary – Goal. Note that, although it is the functions that are labelled, the structure actually consists of the relationships among them. A univariate structure is an iteration of the same functional relationship [...].
- Halliday (1985), Pag. 198