Syntax Tutorial: Phrases & Clauses



Why care about sentence structures like phrases and clauses?

Clauses and phrases are the two main building blocks of sentences. 


A sentence (which must have both a subject and a verb) is a unit of meaning that expresses a "complete thought".

Sentences are essential for clear and unambiguous communication.  This is why experts advise the use "compete sentences", even when writing outlines or creating teaching materials.

Sentence complexity reflects cognitive complexity so it may help to analyze a student's writing by counting the average number of phrases and clauses they use in their sentences. Simple sentences, without a lot of grammatical complexity, may be best for some purposes, such as providing step-by-step directions. For other purposes, such as developing an argument or a compare-and-contrast essay, sentences with more complex structure may be most appropriate.


A PHRASE is a syntactic structure that contains one or more words but does not contain both a subject and a verb (so it is not a sentence). A phrase has one central element, referred to as the head of the phrase.

Heads of phrases can be:

1)    Noun Phrases  

Noun phrases always contain a noun or a pronoun as the head. Noun phrases may be single nouns or pronouns or they may begin with a determiner. Determiners include:  

  • Articles (e.g., a, an, the)
  • Possessives (e.g., my, his, man's, Sam's)
  • Demonstratives (e.g., that, this, those)
  • Quantifiers (e.g., every, another, some)
  • Wh-words (e.g., what, whatever, which)

 Noun phrases can serve different grammatical functions in a sentence:

  • Subject (e.g., The boy was very small.)
  • Object (e.g., The girl read some books.)
  • Complement (e.g., This is what I like.)
  • Adverbial (e.g., We went yesterday.)

2)  Verb Phrases

Verb phrases serve as the main structure of the predicate and include a main verb and any auxiliary verb forms and modifiers that might be attached to it. (e.g., I should have told you about the problem.) (The verb forms infinitives, participles and gerunds can also serve as phrases.)

3)  Adjective Phrases

Adjective phrases have adjectives as the head of the phrase, although there may be one or more modifiers attached to it. (e.g., He has really unsafe habits.)

4)  Adverb Phrases

Adverb phrases have adverbs as the head of the phrase. There might be additional adverbs or adjectives attached to the head adverb in the phrase. (e.g., The children argued all too loudly.) 

5)  Prepositional Phrases

Prepositional phrases begin with a preposition and the preposition is considered the head of the phrase. (e.g., She did really well on the final.) [Some argue that the object of the proposition, the noun to which the preposition refers, should be considered the head of the phrase, but we will consider the preposition the head].



A CLAUSE is a syntactic structure that contains both a subject and a predicate. There are two types of clauses:

1) Independent (main) clauses may stand alone (and when they do stand alone they are the same as a simple sentence) or they may be joined to other clauses by:

  • a coordinating conjunction (e.g., and, or, nor, for, but, yet, so)
  • a conjunctive adverb (e.g., however, therefore, after, because, if)

2)  Dependent (subordinate) clauses can not stand alone (i.e., must be attached to an independent clause) either because they begin with a subordinating conjunction (e.g., if, unless, because) or a relative pronoun (e.g., that, whose, what).

While dependent clauses add meaning to the main clause to which they are attached, they can be deleted without changing the meaning of the main clause.  Some types of dependent clauses include:

  1. Noun (or nominal) clauses (e.g.,This is what he wants.)
  2. Adjective (relative) clauses (e.g.,This is the exercise that we need to do.)
  3. Adverbial clauses (e.g., Do this exercise before the week is over.)
  4. Comparative clauses (e.g., This exercise is harder than the one I did last week.)




Reference: Justice, L.M. and Ezell, H.K. (2002). The Syntax Handbook: Everything You Learned About Syntax…. But Forgot. Eau Claire, Wisconsin: Thinking Publications.


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