What are simple, compound and complex sentences?

simple compound and complex sentencesSimple sentences are formed in English containing an independent clause that forms a grammatically complete action, event or idea. A simple sentence should have a complete noun and verb relationship with any necessary additional information. To make writing more interesting, and lively, English speakers do not onlyuse simple sentences, however. Simple sentences on their own can seem immature, or develop a stop-start rhythm.

We also have combinations of clauses, which can form compound or complex sentences – for longer sentences with more than one verb. These can be used to add variety, and flow, to writing. They can also express more complicated, and connected, ideas.  It is important to develop an understanding for these different types of sentence structure, to write in a more complex, varied, and natural manner.

Simple Sentences

A simple sentence contains a subject and a verb, connected to express a complete grammatical structure. For example:

  • The student read her book.
  • We were playing in the park.
  • It is cold outside.
  • William and Julie have eaten all our cake.

These are all simple sentences as they contain one complete clause. Note that we are discussing a simple sentence specifically – just because the sentence is simple does not mean the tenses, subjects or additional information are simple. The components of the sentences can contain phrases with multiple words, such as prepositional phrases (such as in the park), compound nouns (such as William and Julie) and different verb aspects (such as were playing or have eaten).

 

Compound Sentences

Compound sentences are where more than one independent clause is connected as one grammatical unit.

  • I ate my lunch, and I went to school.

This example is essentially two simple sentences (I ate my lunch. / I went to school.) joined by a conjunction. The conjunctions used for compound sentences include words such as and, but, for, yet, so, nor, and or. These different conjunctions are called co-ordinating conjunctions. They combine two independent clauses, and can represent a relationship between the clauses of a compound sentence, but do not make the clauses dependent on each other. They can, however, represent different relationships between the independent clauses:

  • She studied all night, so she was late for the exam.
  • She studied all night, but she was late for the exam.

The first sentence shows she was late because she studied hard (using so), while the second sentence shows she was late in spite of studying hard (using but, suggesting a contrast).

The separate ideas of a compound sentence can exist independently if you remove the conjunction:

  • The dog fetched the ball and he brought it back.
  • The dog fetched the ball. He brought it back.

When you list more than one independent clause, for instance in a sequence of events, it is not necessary to connect each one with a conjunction. In such an example, you can separate independent clauses with commas.

  • I walked into town, I met with my friends and I bought a new computer.

When the subject is the same in different independent clauses (as with this example), it does not necessarily need to be repeated.

  • I walked into town, met with my friends and bought a new computer.

The independent clauses in compound sentences are often ordered according to time, when showing a listed sequence of actions.

  • I went to the shop, and I bought a bag of fruit, then I came home.

However, if the order of events is not important, and we are not showing cause and effect, then the order of the independent clauses can be flexible.

  • On our holiday, we sunbathed on the beach, we went to many restaurants and we swam in the sea.
  • On our holiday, we swam in the sea, we sunbathed on the beach and we went to many restaurants.

 

Complex Sentences

In a complex sentence, an independent clause is joined to one or more dependent clauses. These are also connected by conjunctions, but they are subordinating conjunctions that create a dependent connection between the clauses. Dependent clauses lack information that would make them a complete idea, for example:

  • when the tide comes in.
  • since I left the UK.

Subordinating conjunctions that create dependent clauses include because, when, since, if, after, and although, and relative pronouns such as that, who and which (which form, more specifically, relative clauses).

  • I cried when I watched that movie.
  • The teacher groaned because the class were bring so noisy.
  • He helped the man who was waiting to cross the road.

As complex sentences are joined in a dependent way, there is no comma between the clauses when the independent clause comes first. However, the dependent clause can come at the beginning of the sentence, separated by a comma:

  • Because of the bad weather, we decided to stay at home.
  • After the game was over, the players were very tired.

The dependent clause can be placed first like this to show sequencing of time, or to build up to the independent clause. This can be done for emphasis, tension or merely to explain things in a logical order.

  • Since the park was closed down, the children have nowhere to play.
  • Although she liked the movie, she was frustrated by the journey home.

There is no correct order of clauses in complex sentences. You can experiment with them, and add greater variety to your writing.

 

Beyond Simple, Compound and Complex Sentences

When you can easily identify clauses and the way they are connected in simple, compound and complex sentences, you can build longer and complicated sentences that combine different simple, compound and complex sentence structure. For example, two sentences joined as a compound can form an independent or dependent clause in a complex sentence:

  • Because the council refused to pay for the building’s repairs, and winter was closing in, the weather was bad and the roof was leaking.

Simple building blocks can lead to complex ideas. As long as you are aware of the simple building blocks, picking out subjects and verbs, and understand their relationships, you can form increasingly elegant, and varied, ideas.

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