Dependent Clauses:  Adverbial, Adjectival, Nominal

Dependent clauses may work like adverbs, adjectives, or nouns in complex sentences.

1. Adverbial clauses

Like a single-word adverb, an adverbial clause describes a verb (in the sentence's main clause) and answers one of these questions

                           where?           why?           how?           when?            to what degree?

An adverbial clause begins with a subordinating conjunction, which makes the clause subordinate (dependent).
Common subordinating conjunctions:

after	in order (that)	unless
although	insofar as	until
as	in that	when
as far as	lest	whenever
as soon as	no matter how	where
as if	now that	wherever
as though	once	whether
because	provided (that)	while
before	since	why
even if	so that
even though	supposing (that)
how	than
if	that
inasmuch as	though
in case (that)	till

  Example of adverbial clause answering when?
       
      When will the flowers bloom?   Answer:  when spring arrives

   Example of adverbial clause answering why?
       
        Why didn't the poor woman have money?  Answer:  because she had lost her job

   Example of adverbial clause answering where?
       
       Where is there fire?   Answer:  where there is smoke

   Example of adverbial clause answering how?
       
        How did he answer the question?  Answer:  as if he knew the subject quite well

       Example of adverbial clause answering to what degree?
       
        To what degree of lateness will Jones arrive?  Answer:  (later) than Smith (will arrive)

    Another example of an adverbial clause answering to what degree?
       
       To what degree is he young?  Answer: (younger) than his brother (is)

Comma use with adverbial clauses

Comma use with adverbial clauses depends upon placement of the adverbial clause.
If the adverbial clause introduces the sentence, place a comma between it and the main clause.
       

If the adverbial clause follows the main clause in a sentence, do not place a comma between the two.
       

2.  Adjectival clauses

Like a single-word adjective, an adjectival clause describes a noun (in the sentence's main clause) and answers one of these questions

                                     which one?                   what kind?      

An adjectival clause usually begins with a relative pronoun, which makes the clause subordinate (dependent).
Common relative pronouns:
                  that         which         who        whom        whose
NOTE:  Use who, whom, and whose to describe people.
               Use that and which to describe things.
Adjectival clauses always follow the person, place, or thing they describe, usually immediately.

   Example of adjectival clause answering which one?
       
        Which book did Joe read?  Answer:  the one that I gave him

   Example of adjectival clause answering what kind?
       
        What kind of politician has the support of the people?  Answer:  one who is trustworthy

Adjectival clauses may also begin with selected subordinating conjunctions:
                when  - to describe a time
       

                where  - to describe a place     
       

               why - to describe a reason
       

Comma use with adjectival clauses

Comma use with adjectival clauses depends upon essentiality of the adjectival clause.
If the adjectival clause is essential (or "needed"), no commas should be used to separate it from the main clause.  
Generally, essential adjectival clauses should not begin with which.
    Examples
       
       
    Since the adjectival clauses in the above examples are needed to clarify the noun that they describe, they are essential and should not be separated from the rest of the sentence with commas.

If the adjectival clause is nonessential (or "not needed"), commas should separate it from the main clause. 
 Nonessential adjectival clauses should not begin with that.
    Examples
       
       
    Since the adjectival clauses in the above examples are not needed to clarify the noun that they describe, they are nonessential and should be separated from the rest of the sentence with commas.
Note the difference between the sentences in each pair:
  
  

 

3.  Nominal Clauses

Like a noun, a nominal clause names a person, place, thing, or idea.  A nominal clause may function in a sentence as any of the following:
     subject                      subjective complement             appositive               object of preposition                  direct object             indirect object                             retained object


Nominal clauses may begin with interrogatives:
    who     whom   what    which     whoever      whomever     whatever     when    where     how   why
An  interrogative beginning a nominal clause has a function within the nominal clause.
Each of the  following examples illustrates

•    a nominal clause
•    the function of the nominal clause within the sentence
•    the function of the interrogative within the nominal clause

   Nominal clause as subject in sentence 
       

   Nominal clause as subjective complement in sentence
       

   Nominal clause as object of preposition in sentence
       

   Nominal clause as direct object in sentence   
       

   Nominal clause as indirect object in sentence
       

   Nominal clause as retained object in sentence 
       

Nominal clauses may also begin with expletives:
         that        whether       if
An expletive beginning a nominal clause has no function within the nominal clause.
   Nominal clause beginning with expletive that
       

   Nominal clause beginning with expletive whether
       

   Nominal clause beginning with expletive if