Noun clauses are clauses that function as nouns. Remember that clauses can be either dependent or independent. Noun clauses, like nouns, can be used as either subjects or objects. Noun clauses are therefore dependent clauses as as subject or object can not stand alone as a sentence.
Nouns are subjects or objects:
Baseball is an interesting sport. Noun: Baseball = subject
Tom would like to buy that book. Noun: Book = object
Noun clauses are subjects or objects:
I like what he said. Noun clause: ... what he said = object
What he bought was awful: Noun clause: What he bought ... = subject
Noun clauses can also be an object of a preposition:I'm not looking for what he likes. Noun clause: ... what he likes = object of preposition 'for'
We decided to look into how much it costs. Noun clause: ... how much it costs = objects of preposition 'into'
Noun Clauses as Compliments
Noun clauses can play the role of a subject compliment. Subject compliments provide a further description, or clarification of a subject.
Harry's problem was that he couldn't make a decision.
Noun clause: ... that he couldn't make a decision. = subject compliment of 'problem' describing what the problem was
The uncertainty is whether he will attend or not.
Noun clause: ... whether he will attend or not. = subject compliment of 'uncertainty' describing what is uncertain
Noun clauses can play the role of an adjective complement. Adjective compliments often provide a reason why someone or something is a certain way. In other words, adjective compliments provide additional clarification to an adjective.
I was upset that she couldn't come.
Noun clause: ... that she couldn't come = adjective compliment explaining why I was upset
Jennifer seemed angry that he refused to help her.
Noun clause: ... that he refused to help her. = adjective compliment explaining why Jennifer seemed angry
Noun Clause Markers
Markers are what introduce noun clauses. These markers include:
that if, whether (for yes / no questions) Question words (how, what, when, where, which, who, whom, whose, why) Ever words beginning with 'wh'(however, whatever, whenever, wherever, whichever, whoever, whomever)
I didn't know that he was coming to the party. Could you tell me whether she can help us. The question is how to finish on time. I'm sure I will enjoy whatever you cook for dinner.
Noun Clauses Used with Common Phrases
Noun clauses beginning with question words or if/whether are often used with common phrases such as:
I don't know ... I can't remember ... Please tell me ... Do you know ...
This use of noun clauses is also known as indirect questions. In indirect questions, we use a phrase to introduce a question with a short phrase and turn the question into a noun clause in statement order.
When will he return? Noun clause / indirect question: I don't know when he will return.
Where are we going? Noun clause / indirect question: I can't remember where we are going.
What time is it? Noun clause / indirect question: Please tell me what time it is.
When does the plan arrive? Noun clause / indirect question: Do you know when the plane arrives?
Yes / No Questions
Yes / no questions can be expressed as noun clauses using if / whether:
Are you coming to the party? Noun clause / indirect question: I don't know if you are coming to the party.
Is it expensive? Noun clause / indirect question: Please tell me whether it is expensive.
Have they lived there long? Noun clause / indirect question: I'm not sure if they have lived there long.
Special Case of 'That'
The noun marker 'that' which introduces noun clauses is the only marker that can be dropped. This is only true if 'that' is used to introduce a noun clause in the middle or at the end of the sentence.
Tim didn't know that she was available. OR Tim didn't know she was available.