A noun clause, like other clauses, is a group of words that includeS a subject and a verb. It is a subordinate clause. As a dependent clause, it must be connected to an independent clause (main clause) to form a complete sentence. A noun clause functions as a noun, which means it can be a subject, direct object, indirect object, object of a preposition, predicate nominative, or appositive. One point to bear in mind is a noun clause is not a noun modifier.
Noun clauses usually begin with words called relative pronouns such as how, that, what, whatever, when, where, which, who, whoever, and why. The most common word among them is that.
Examples of noun clause showed here in bold. The relative pronouns used are how, that, and why.
A noun clause has its own subject and verb. There must be a word, a relative pronoun, to connect the noun clause to the rest of the sentence. The connecting word (also called connector) comes before the subject and the verb of the noun clause. The following examples use the relative pronouns where, that, who, and when.
Noun clauses can be the subject, direct object, indirect object, object of preposition, object of verbal noun (gerund) or complement. The noun clauses in the following examples are in bold.
A noun clause is used as a predicate complement (boldfaced) to complete a sentence.
Converting a question into a noun clause
The relative pronouns if and whether can be used to change a question – usually a yes/no question – into a noun clause.
Subjunctive in noun clauses