Noun clause is a dependent clause that functions as a noun (a noun).
This noun clause can function as subject or object in a clause or a phrase in another.
It acts as a noun, it can be replaced with the pronoun “it”.
Example:
  • I forgot the fact. (noun)
  • I forgot it. (pronoun)
  • I forgot that the fact was very important. (noun clause)
Formula Noun Clause
Noun clause can be preceded by a noun clause markers in the form of question word, if or Whether, and that. As examples of noun clause to another clause, along with details of his marker can be seen in the following table.
Marker
Details
Example of setence  Noun Clause
Question Words Question word:
what(ever), what (time, kind, day, etc),
who(ever),
whose,
whom(ever),
which(ever),
where(ever),
when(ever),
how (long, far, many times, old, etc)		 The class listened carefully what the teacher instructed.
The kitten followed wherever the woman went.
Many people imagine how many time the man was failed before success.
(Banyak orang membayangkan berapa kali pria itu gagal sebelum sukses.)
if or whether usually used to sentence answer to the question yes / no question Where does Arrifin live?
I wonder if he lives in West Jakarta.
Is Andy live on Dewi Sartika Street?
I don’t know if he live on Dewi Sartika Street or not.
that usually that-clause to mental activity. Here’s a list of the verb in the main clause is usually followed by that-clause: Assume,believe, discover, dream, guess, hear, hope, know, learn, notice, predict, prove, realize, suppose, suspect, think I think that the group will arrive in an hour.
Many people proved that the man was a big liar.
Fungsi Noun Clause
Here is an example sentence of each noun clause function.

Fungsi
Contoh Kalimat Noun Clause
Subject of a Verb What she cooked was delicious.
That today is his birthday is not right.
Subject complement The fact is that she is smart and dilligent.
A teacher must be whoever is patient.
Object of a Verb Diana believes that her life will be happier.
I want to know how Einstein thought.
Object of a preposition The girl comes from where many people there live in poverty.
He will attend the party with whichever fits to his body.