Sentence clause structure

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In grammar, clause structure refers to the classification of sentences based on the number and kind of clauses in their syntactic structure. Such division is an element of traditional grammar.

A simple sentence consists of only one clause. A compound sentence consists of two or more independent clauses. A complex sentence has at least one independent clause plus at least one dependent clause.[1] A set of words with no independent clause may be an incomplete sentence, also called a sentence fragment.

A sentence consisting of at least one dependent clauses and at least two independent clauses may be called a complex-compound sentence or compound-complex sentence.[unreliable source?]

Sentence 1 is an example of a simple sentence. Sentence 2 is compound because "so" is considered a coordinating conjunction in English, and sentence 3 is complex. Sentence 4 is compound-complex (also known as complex-compound). Example 5 is a sentence fragment.

  1. I like pumpkin pie.
  2. I don't know how to bake, so I buy my sweets.
  3. I enjoyed the apple pie that you bought for me.
  4. The dog lived in the garden, but the cat, who was smarter, lived inside the house.
  5. What an idiot.

The simple sentence in example 1 contains one clause. Example two has two clauses (I don't know how to bake and I buy my sweets), combined into a single sentence with the coordinating conjunction so. In example 3, I enjoyed the apple pie is an independent clause, and that you bought for me is a dependent clause; the sentence is thus complex. In sentence 4, The dog lived in the garden and the cat lived inside the house are both independent clauses; who was smarter is a dependent clause. Example 5 features a noun phrase but no verb. It is not a grammatically complete clause.

Simple sentences

A simple sentence structure contains one independent clause and no dependent clauses.[2]

  • I run.

This simple sentence has one independent clause which contains one subject, I, and one predicate, run.

  • The girl ran into her bedroom.

This simple sentence has one independent clause which contains one subject, girl, and one predicate, ran into her bedroom. The predicate is a verb phrase that consists of more than one word.

  • In the backyard, the dog barked and howled at the cat.

This simple sentence has one independent clause which contains one subject, dog, and one predicate, barked and howled at the cat. This predicate has two verbs, known as a compound predicate: barked and howled. This compound verb should not be confused with a compound sentence. In the backyard and at the cat are prepositional phrases.

Compound sentences

A compound sentence is composed of at least two independent clauses. It does not require a dependent clause. The clauses are joined by a coordinating conjunction (with or without a comma). a semicolon that functions as a conjunction, a colon instead of a semicolon between two sentences when the second sentence explains or illustrates the first sentence and no coordinating conjunction is being used to connect the sentences, or a conjunctive adverb preceded by a semicolon. A conjunction can be used to make a compound sentence. Conjunctions are words such as for, and, nor, but, or, yet, and so. Examples:

  • I started on time, but I arrived late.
  • I will accept your offer or decline it; these are the two options.
  • The law was passed: from 1 April, all cars would have to be tested.
  • The war was lost; consequently, the whole country was occupied.

The use of a comma to separate two independent clauses without the addition of an appropriate conjunction is called a comma splice and is generally considered an error (when used in the English language).[2] Example:

  • The sun was shining, everyone appeared happy.

Complex and Compound-Complex sentences

A Complex sentence has one or more Dependent clauses (also called subordinate clauses). Since a dependent clause cannot stand on its own as a sentence, complex sentences must also have at least one independent clause. A sentence with two or more independent clauses plus one or more dependent clauses is called compound-complex or complex-compound.

In addition to a subject and a verb, dependent clauses contain a subordinating conjunction or similar word. There are a large number of subordinating conjunctions in English. Some of these give the clause an adverbial function, specifying time, place, or manner. Such clauses are called adverbial clauses.

  • When I stepped out into the bright sunlight, from the darkness of the movie house, I had only two things on my mind. (S. E. Hinton, The Outsiders)

This complex sentence contains an adverbial clause, When I stepped out into the bright sunlight from the darkness of the movie house. The adverbial clause describes when the action of the main clause, I had only two things on my mind, took place.

A relative clause is a dependent clause that modifies a noun or noun phrase in the independent clause. In other words, the relative clause functions similar to an adjective.

In the first example, the restrictive relative clause who has been deceived specifies or defines the meaning of him in the independent clause, Let him complain. In the second example, the non-restrictive relative clause who have never known your family describes you in the independent clause, You see them standing around you.

A noun clause is a dependent clause that functions like a noun. A noun clause may function as the subject of a clause, or as a predicate nominative or an object.

In this sentence the independent clause contains two noun clauses. The noun clause What she had realized serves as the subject of the verb was, and that love was that moment serves as complement. The sentence also contains an adverbial clause, when your heart was about to burst.

Incomplete sentence

An incomplete sentence, or sentence fragment, is a set of words which does not form a complete sentence, either because it does not express a complete thought[1] or because it lacks some grammatical element, such as a subject or a verb.[3] A dependent clause without an independent clause is one example of an incomplete sentence.

Some prescriptive grammars[4] consider sentences starting with a conjunction such as but or and to be incomplete sentences, but this style prescription has "no historical or grammatical foundation".[5] Computer grammar checkers often highlight incomplete sentences. If the context is clear from the rest of the paragraph, however, an incomplete sentence may be considered perfectly acceptable English.[6][unreliable source?]


  1. 1.0 1.1 Huddleston, Rodney (1984). Introduction to the Grammar of English. Cambridge University Press. ISBN 978-0-521-29704-2.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. 2.0 2.1 Rozakis, Laurie (2003). The Complete Idiot's Guide to Grammar and Style pp. 167–168. Alpha. ISBN 1-59257-115-8.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  3. Sinclair, Christine (2007). Grammar: Getting it Right. McGraw-Hill. ISBN 978-0-335-22008-3.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  4. e.g. H. W. Fowler in Modern English Usage on BUT, p. 60 in the first edition.
  5. The Chicago Manual of Style (16th ed.). Chicago: University of Chicago Press. 2010. p. 257. ISBN 978-0-226-10420-1.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  6. "Sentence fragments". 20 December 2015. Retrieved 22 March 2014.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>

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