a NOMINAL CLAUSE is a dependent clause that functions as a noun, and so it can be the subject, the object, or a complement within a sentence.
Nominal Clauses as Subjects
There are several kinds of NOMINAL CLAUSES, but the two most common types begin with THAT, or a WH word like WHAT or WHERE, and these are called WH-clauses:
That we were late to class, really upset the teacher.(THAT nominal clause)
In this case the subject is the noun clause That we were late to class
What I had forgotten was that I had a test today.(WH nominal clause)
In this case the subject is the noun clause What I had forgotten was that
Nominal Clauses as Direct Objects
You must choose which flavor of ice cream you want.(WH nominal clause)
In this case, the verb is CHOOSE, so the object of the verb is which flavor of ice cream you want.
Sometimes nominal clauses can begin with question words like:
who, whom, what, which, whoever, whomever, whatever, when, where, how, or why.
Who he spends his time with is of no interest to me.(nominal clause)
You can buy whatever you fell you can afford.(nominal clause)
Nominal clauses can also begin with words like
whether and if:
Whether he calls or not is of no interest to me.(nominal clause)
I don't care if he calls or not.(nominal clause)