Complement Clause in Grammar

In English grammar, a complement clause is a subordinate clause that serves to complete the meaning of a noun or verb in a sentence. Also known as a complement phrase (abbreviated as CP).

Complement clauses are generally introduced by subordinating conjunctions (also known as complementizers) and contain the typical elements of clauses: a verb (always), a subject (usually), and direct and indirect objects (sometimes).

Observations and Examples

• "A complement clause is a clause which is used as the complement of some other word (typically as the complement of a verb, adjective or noun). Thus, in a sentence such as He never expected that she would come, the clause that she would come serves as the complement of the verb expected, and so is a complement clause."
  (Andrew Radford, Syntax: A Minimalist Introduction. Cambridge University Press, 1997)
• Complement Clauses as Noun Clauses
  "Complement clauses can be that-clauses, wh-clauses, ing-clauses or infinitive clauses. The most common type is a complement clause following a verb. . . . In versions of grammar that use the concept of complement clause, it largely or entirely replaces the concept of nominal clause (or noun clause) referring to a clause that can occur in positions where noun phrases occur. For example, in I'd like to carry on, the infinitive complement clause is the object of the main clause, filling a position where a noun phrase could occur."
  (Geoffrey N. Leech, A Glossary of English Grammar. Edinburgh University Press, 2006)
• Types of Complement Clauses
  "Recently, linguists working in the influential theory known as 'generative grammar' have used the term 'complement' to refer to variously closely related kinds of subordinate clause, namely:
  1. Subordinate clauses which on their own serve as the direct object of verbs such as believe, tell, say, know, and understand; the subordinate clauses are the complements of these verbs.
  2. Subordinate clauses which modify various nouns such as story, rumour, and fact, and adjectives such as proud, happy, and sad; the subordinate clauses are the complements of these nouns and adjectives.
  3. Subordinate clauses which on their own act as the subject of sentences with such predicates as be a pity, be a nuisance, be unfortunate, seem, and happen. These clauses are called 'subject complements' or 'subject complement clauses.'
  . . . Sometimes the term 'complement clause' is extended to the adverbial type of subordinate clause as well."
  (James R. Hurford, Grammar: A Student's Guide. Cambridge University Press, 1994)
• Examples
  - "You may call me Bob. From now on, I am Bob. I can assure you that Bob is quite proficient at electronic data manipulation. Without question one of the world's finest."
  (Ted Dekker, Heaven's Wager. WestBow Press, 2000)
  - "Imagine that Frank is a fan of his town's soccer club. He always wears the same shirt when he watches his club play. He believes that they will win if he puts on the shirt at just the right time before the game starts."
  (Joshua James Kassner, Rwanda and the Moral Obligation of Humanitarian Intervention. Edinburgh University Press, 2013)
  - "She said she was approaching 40, and I couldn't help wondering from what direction."
  (Bob Hope)
  - "The fact that the adult American Negro female emerges a formidable character is often met with amazement, distaste and even belligerence."
  (Maya Angelou, I Know Why the Caged Bird Sings, 1969)