A clause may contain a formative which marks its information structure and, speficially, its focus. Such a formative may be synchronically identical with a copula or diachronically stem from one. The origin of such a construction is a cleft-construction, either a cleft-sentence or a pseudo-cleft sentence. In the source construction, the copula may conjugate for all of its morphological categories. In the course of its grammaticalization, it may reduce to an invariable thematic structure articulator and, more specifically in certain cases, a focus marker.

The source of the construction is a complex clause, formed by the respective rules of syntax. The result is monoclausal. The original construction is reanalyzed on the model of the simple clause (which is always available). Consequently, on the one hand, the result construction no longer obeys the same rules of grammar that are necessary and sufficient for the source construction. In other words, not all clauses containing the thematic structure articulator bear a regular paradigmatic relation to a cleft or pseudo-cleft construction.

On the other hand, the resulting construction shows traits of persistence of the original configuration. Among these are the following facts:

• The position of the focus marker vis-à-vis the focal component reflects the position of the copula vis-à-vis the predicate complement in its language.
• Even if the copula is just a thematic structure articulator, it still fits this function in a special way: The relation between the subject and the predicate as mediated by the copula is a static (non-transitory) relation; and so is the relation of the focal component applying to the open proposition coded by the extrafocal clause (Zhan & Sun 2013).