Clauses can be classified according to a distinctive trait that is a prominent characteristic of their syntactic form.
The position of the finite verb is one major trait used for classification, and the appearance of a specific type of focusing word (e.g. 'Wh'-word) is another.
These two criteria overlap to an extent, which means that often no single aspect of syntactic form is always decisive in deciding how the clause functions.
Standard SV-clauses can also be interrogative or exclamative, however, given the appropriate intonation contour and/or the appearance of a question word, e.g.
Examples like these demonstrate that how a clause functions cannot be known based entirely on a single distinctive syntactic criterion.
SV-clauses are usually declarative, but intonation and/or the appearance of a question word can render them interrogative or exclamative.
The wh-word focuses a particular constituent, and most of the time, it appears in clause-initial position.
The b-sentences are direct questions (independent clauses), and the c-sentences contain the corresponding indirect questions (embedded clauses): One important aspect of matrix wh-clauses is that subject-auxiliary inversion is obligatory when something other than the subject is focused.
Another important aspect of wh-clauses concerns the absence of subject-auxiliary inversion in embedded clauses, as illustrated in the c-examples just produced.
Embedded clauses can be categorized according to their syntactic function in terms of predicate-argument structures.
This confusion is due in part to how these concepts are employed in the phrase structure grammars of the Chomskyan tradition.
Extending this convention to the clausal categories occurred in the interest of the consistent use of labels.
There is a progression in the size and status of syntactic units: words < phrases < clauses.
The characteristic trait of clauses, i.e. the presence of a subject and a (finite) verb, is absent from phrases.
Finally, some modern grammars also acknowledge so-called small clauses, which often lack a verb altogether.
The subject-predicate relationship that has long been taken as the defining trait of clauses is fully present in the a-sentences.
The fact that the b-sentences are also acceptable illustrates the enigmatic behavior of gerunds.
The to-infinitives to consider and to explain clearly qualify as predicates (because they can be negated).
The subjects she and he are dependents of the matrix verbs refuses and attempted, respectively, not of the to-infinitives.
PRO-theory is particular to one tradition in the study of syntax and grammar (Government and Binding Theory, Minimalist Program).
A typical small clause consists of a noun phrase and a predicative expression,[6] e.g.
While the subject-predicate relationship is indisputably present, the underlined strings do not behave as single constituents, a fact that undermines their status as clauses.