Noun Clause

A noun clause is a group of words that include a subject and a verb, and it functions as a noun. A noun clause is a subordinate clause, which means it is not a complete statement. As a dependent clause, it must connect to an independent clause (main clause). Noun clauses usually begin with words 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 shown in bold.

• Why he said he would not get married, nobody knows.
• He told me that he had shot someone.
• You can go if you do not like being here.
• Ask him whether he has drunk from your glass or mine by mistake.

Noun clauses can be the subject, object, object of preposition, complement, etc. The noun clauses in the following examples are in bold.

• That the brothers are triplets is amazing. (Subject)
• We don’t know what songs she often sings. (Object)
• The book is about where the dinosaurs laid their eggs. (Object of preposition)
• He is what we would call a misogynist. (Complement)

A noun clause has its own subject and verb.

• They know where I often fly my kites.
  The noun clause is where I often fly my kites with I being the subject of the noun clause, and fly is the verb.

A noun clause must have a word to connect the noun clause to the rest of the sentence. The connecting word (connector) comes before the subject and the verb of the noun clause. The following examples use the connecting words that, who, and when.

• Most people know that a spider has eight legs.
• The police were investigating who the serial killer was.
• I don’t know when the birds built their nest in the roof.

Subjunctive in noun clauses

We use subjective verbs in sentences to express or stress wishes, importance, or urgency.  A subjunctive verb usually appears in a noun clause beginning with that, and it uses the simple form of a verb that does not have the present, past or future forms. The subjunctive verb is neither singular nor plural.

• The leader demands that we treat him like a god.
• We insisted that he honour the terms of the agreement.
• The father recommended that she not go to the cinema alone.
• It is important that everyone be told the truth.
• His mother suggested that he see/should see a doctor

sumber : http://www.myenglishgrammar.com/lesson-17-clauses/4-noun-clause.html