This post explains complement clause and clears the confusion between complement clause and noun clause.
What is complement clause?
A complement clause is a dependent clause that completes the meaning of a noun, adjective, verb, or preposition. It is essentially a noun clause. Jim Miller, in An Introduction to English Syntax, calls complement clause a ‘contemporary label’ for noun clause. And Geoffrey Leech, in Glossary of English Grammar, mentions, “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.”
Old wine in the new bottle!
Clause gets a new name! Why leave the introductory word behind? Words that introduce complement clause are called complementizers. As you might have guessed, they’re words that introduce noun clause: that, if, whether, and wh-words.
Using the term complement changes the lens through which we see the function of the clause: We now see it as a completer of the meaning of words and phrases and not as a noun filling in different slots such as subject, object, etc.
Let’s look at what all a complement clause can complement. You can tally these with different functions of a noun clause, and you’ll hardly find any difference. We’re essentially looking at the same thing through a different lens.
1. Verb-complement clause
Different types of verbs can be complemented in different ways. The four types of verbs combined (linking, mono-transitive, complex transitive, and di-transitive) can be complemented in six different ways. But if you consider complementation by only clauses, options narrow down to two as some positions don’t or rarely take clauses.
1.1 Verb-complement clause (linking verb)
Also known as subject-complement clause, it complements a linking (or copular) verb. Examples:
The answer isn’t what you think. [The linking verb be is incomplete in meaning without the underlined verb-complement clause]
Our problem is whom we trust.
The problem is that the test is not full-proof.
1.2 Verb-complement clause (mono-transitive verb)
The most common verb-complement clause, it complements a mono-transitive verb. Since a clause rarely is an indirect object, di-transitive verb can be considered a part of mono-transitive verb as far as complementation by clause is concerned. Examples:
Studies show that human productivity drops off significantly after 5-6 hours of intense mental work. [The mono-transitive verb show is incomplete in meaning without the underlined verb-complement clause]
Scientists believe that Covid is going to stay with us for at least few years.
Some wonder if there is intelligent life like us on other planets.
We don’t know who our real friends are till adversity strikes.
Drunkenness reveals what soberness conceals.
Note: Some grammar books also consider a clause in subject position to be complement of verb, as subject too is essential for the meaning of verb.
2. Preposition-complement clause
The preposition-complement clause completes the meaning of a preposition, always following the preposition it complements. In traditional grammar, this clause is known as object of preposition clause. Examples:
We should refrain from speculating and jumping to conclusion on why someone behaved in certain way.
Don’t copy others to fit into what others want to see.
You’ve to face the consequences regardless of who you are.
3. Adjective-complement clause
The adjective-complement clause completes the meaning of an adjective, almost always following the adjective it complements. The adjectives that are complemented by such clause are rarely attributive. Examples:
It’s not clear if the match will get a go-ahead. [The adjective clear is incomplete in meaning without the underlined adjective-complement clause]
I’m not sure if he’ll join us for dinner.
I felt sorry that your mother met with an accident.
I’m happy that you’ve decided to come.
After a week into the tournament, it’s clear who is winning and who is not.
Here we considered only clauses as complements. If you want to learn the entire range of phrases and clauses that can complement adjectives, have a look at post on adjective complements.
4. Noun-complement clause or Appositive clause
The noun-complement clause completes the meaning of a noun, almost always following the noun it complements. This clause works with only few nouns, mainly reporting nouns such as idea, fact, comment, remark, statement, claim, argument, assumption, proof, possibility, and response. Examples:
Nobody believed his statement that he saw a UFO. [The noun statement is incomplete in meaning without the underlined noun-complement or appositive clause]
New paleontological discoveries have changed our belief that homo sapiens were the only human species some 30,000 years ago.
The fact that he is not present in such an important meeting speaks volumes of his interest in the project.
Earlier astronomers put forth the idea that earth was the center of universe.
His remark that Darwin’s theory of evolution is not correct expectedly created a controversy.
Here we considered only clauses as complements. If you want to learn the entire range of phrases and clauses that can complement nouns, have a look at post on noun complements.
