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 "complete 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 heads of phrases.)

3)  Adjective Phrases

Adjective phrases have adjectives as the head of the phrase. 

Adjectives identify or describe people, places or things. they are usually positioned before the noun or pronoun they modify.  

There may be one or more adjective modifying a noun or pronoun. (e.g., In the sentence, "He has risky, unsafe habits" both "risky" and "unsafe" are adjectives modifying the noun "habits".  It would make sense to say: "He has risky habits." and "He has unsafe habits."

Adjectives can also modify other adjectives (e.g., In the sentence, "He has really unsafe habits.", the adjective "really" modifies the adjective "unsafe" and not the noun "habits".  It would not makes sense to say: "He has really habits." ) 

4)  Adverb Phrases

Adverb phrases have adverbs as the head of the phrase.

Adverbs provide a description of how, where, when, in what manner and to what extent something is done or happens. So, adverbs modify the action.  (e.g., In the sentence, "He plays golf extremely well." both "extremely" and "well" are adverbs because they modify the action, "plays".)

There might be more than one adverbs or adjectives attached to the head adverb in the phrase. (e.g., The sentence, "The children argued all too loudly." has an adverb phrase, "all too loudly" that describes the action, "argued". ) 

5)  Prepositional Phrases

Prepositional phrases begin with a preposition and the preposition is considered the head of the phrase. (e.g., In the sentence, "She did really well on the final." the preposition "on" is the head of the prepositional phrase "on the final".)

Prepositions connect the people, objects, time and locations of a sentence by expressing position and movement, possession, time and/or how an action is completed. 

Caution!  You must look at the role a word is playing in the sentence to determine its part of speech! Some function words (like "to") can serve different functions. For example:

  • "I like to play chess."  (The word "to" is part of the verb, "to play". The phrase "to play chess" is an infinitive verb phrase.)
  • "I like traveling to chess tournaments." (The word "to" is a preposition expressing location, connecting "traveling" and "tournaments". The phrase "to chess tournaments" is a prepositional phrase.)

[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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