Clefting is a syntactic operation applied to a simple clause S₀ which contains a focal component F. The operation cleaves S₀ into a complex clause consisting of two simple clauses S_↴ and ^↴S, where ^↴S depends on S_↴. S_↴ comprises F in predicate position, while ^↴S contains the extrafocal portion of S₀. Since F has been extracted, the extrafocal portion is an open proposition. No interpropositional relation is associated with the dependency between the two clauses since the only function of clefting is to highlight F while at the same time backgrounding the extrafocal portion of S₀.

Given the two varieties of focusing, viz. insistence and suspension, with the associated orders ‘F - extrafocal portion’ and ‘extrafocal portion - F’, resp., there are two basic varieties of clefting:

1. For insistence, the order of the two clauses is S_↴ - ^↴S. In the syntactically regular, most elaborate variety of insistence, S_↴ is a nominal or copula clause with an empty or cataphoric subject and F in predicate position, while the extrafocal clause ^↴S may bear structural marks of subordination (a). This variety is traditionally called cleft-sentence.
2. For suspension, the order of the two clauses is ^↴S - S_↴. In the syntactically regular, most elaborate variety of suspension, ^↴S is a headless relative clause oriented towards the extracted F, while S_↴ is a nominal or copula clause with ^↴S in subject and F in predicate position (b). This variety is traditionally called pseudo-cleft sentence.

If F is a nominal syntagma, ^↴S in the cleft-sentence may have the form of a relative clause, too (substituting that in a by whom). If F is an adverbial, ^↴S cannot be a relative clause, but can only be introduced – if at all – by the universal subordinator ().

Given that sentence-initial topics precede the focal component and, moreover, can be stacked, both varieties of clefting can be complicated by preceding topical material ().

In the case of the cleft-sentence of a, this leads to a configuration where some topical material precedes the focus while other topical material follows it.

Both varieties of clefting are subject to grammaticalization. Then typically part or all of the structural apparatus necessary for complex sentence formation, subordination, open clause formation and (in S_↴) formation of a clause with a nominal predicate is suppressed. The result is a monoclausal focus construction; and if one of the original structural devices survives, it will appear as a focus marker. Examples are in the section on the grammaticalization of the Mandarin copula.

A more extensive treatment of clefting is in the section on complex sentence formation.

Creissels, Denis 2021, ‘Remarks on the grammaticalization of identificational clefts’. Faits de Langue 52.1: 13-31.