Complements
Complements are often required to form a grammatically complete and meaningful sentence. Consider the following examples, where grammatically incorrect sentences are indicated (Haegeman & Guéron, 1998, pp. 21-22):
From these examples, it is clear that the verb abandon must be followed by a noun phrase (NP) such as the project. If the verb abandon is not paired with an NP, the resulting sentence is ungrammatical (b, c). Therefore, to construct a grammatical sentence with the verb abandon, it must include a complement of the NP category.
Verb complement clauses
Verb complement clauses are dependent clauses that serve to complete the meaning of a verb in a main clause (e.g., I think that this doc looks good; that-clause functions a complement to the verb think). These clauses are also called nominal clauses because they frequently occupy a noun phrase slot in the sentence, acting as subjects, objects, or predicatives. Depending on the controlling predicate, they can be found in both pre-predicate (subject) and post-predicate (e.g., direct object) positions (For more information, see Chapter 9).
However, complement clauses can also complete the meaning of an adjectival predicate rather than a verb in the main clause (e.g., I've gotta be careful that I don't sound too formal). Here, the term predicate refers to both lexical verbs and copula+adjective combinations capable of governing a complement clause. This aspect will be further explored in the section on other phrase constituent: adjective complement.
There are four types of verb complement clauses: (1) that-clause, (2) wh-clause, (3) to-infinitive clause, and (4) ing-clause. In this section, types (1) and (2) will be highlighted as complexity features because they are finite clauses, while types (3) and (4) will be discussed in the section on non-finite clause constituent verb complements.