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Expanding Sentences

Writing is a very important aspect of communication. In fact, it has allowed our world to continue to develop and grow. In the course of this process, writing itself has had to evolve. One characteristic of more advanced writing is using subordination and coordination.

These two terms deal with turning simple sentences into complex ones. Subordination involves adding subordinating clauses, which use a subordinating conjunction. This is a very technical definition and a more detailed explanation will be given later in this lesson. Coordination involves expanding sentences by adding information. This lesson will explain these two processes and detail how to avoid making errors while creating more complex sentences.


The first term we will examine is subordination. Earlier, you saw that the definition for subordination was adding subordinating clauses, which use a subordinating conjunction. I’m sure this definition does not really clear things up for you. Let’s look closer at what subordinating clauses and conjunctions are.

First, we need to review what makes up a complete sentence. A subject, or a noun doing the action, and a predicate, or the verb and the rest of the words, are needed in order to have a complete sentence. Look at this simple sentence: ‘I was chased by a dog.’ What is the subject? ‘I’ is the subject. What is the predicate? ‘Was chased’ is the action, or verb, and the words that follow are all a part of the predicate.

Subordinate Clauses

If everyone wrote in these types of simple sentences, so much detail and explanation would be missing. Adding in clauses, which in simple terms are groups of words, can supply some of that missing information. For example, this sentence, ‘While running through my neighbor’s yard, I was chased by a dog,’ gives a little more detail into why the dog may be chasing this person.

What clause was added to the original sentence? ‘While running through my neighbor’s yard’ is the clause that was added. This is an example of a subordinate clause. Subordinate clauses cannot stand alone. Alone they are fragments, or incomplete sentences. Subordinate clauses always begin with a subordinating conjunction. Remember, a conjunction is a connecting word, so a subordinating conjunction is a word that connects a subordinate clause to another clause. Some common subordinating conjunctions are ‘if,’ ‘since,’ ‘because,’ and ‘although.’

Look again at the definition for subordination: adding subordinating clauses, which use a subordinating conjunction. This sentence shows subordination: ‘While running through my neighbor’s yard, I was chased by a dog.’ The subordinating conjunction is the word ‘while,’ which begins the whole subordinating clause, ‘while running through my neighbor’s yard.’ The most common error with using subordinating clauses is simply leaving the clause as its own sentence. This would be a fragment and should never happen in your writing. Secondly, look at the punctuation that connects the two clauses. Another common error is forgetting to add in the comma after the subordinating clause.

Look at these other examples of sentences using subordination. Try to identify the subordinating conjunction. Also, note the use of the comma to connect the clauses.

  • ‘If Katie gets an A on her final, she will have a B in the class.’ (subordinating conjunction is ‘if’)
  • ‘Since there is no chance of rain tomorrow, we will have a picnic in class.’ (subordinating conjunction is ‘since’)
  • ‘Although we never discussed it, the essay will be due next week.’ (subordinating conjunction is ‘although’)


The second way to expand sentences is coordination, which involves adding information to parts of the sentence. This is different from adding whole clauses in that sometimes only one or two words will be added. For example, you can use coordination to add a second subject to sentences. Look at this sentence: ‘Steve ran a mile.’ Add in another subject to make the sentence, ‘Steve and Mike ran a mile.’ Notice that you had to insert the conjunction ‘and’ and that no comma was inserted. When you add in a subject, never use a comma.

You can also add in other parts, like a second verb, to your sentence. For example, ‘Steve ran a mile and biked two miles.’ In this case, the predicate was expanded to include the second action ‘biked.’ Again, notice the conjunction ‘and’ is used and no comma was inserted. When adding to subjects and verbs, never add a comma.

Coordination Between Sentences

Lastly, you can use coordination to combine two complete sentences. Remember, these rules only apply if both sentences are complete, which means both have a subject and a predicate. For example, ‘Steve ran a mile.’ ‘Mike biked two miles.’ Both these sentences have a subject and a predicate. To connect these two sentences, you can use one of two methods. First, add a comma and a conjunction. ‘Steve ran a mile, and Mike biked two miles.’ Or, you can use a semicolon ‘Steve ran a mile; Mike biked two miles.’

The most common error when using coordination with two complete sentences is called a comma splice. This means only a comma was used to combine the two. ‘Steve ran a mile, Mike biked two miles.’ is a comma splice. You either must add a conjunction or replace the comma with a semicolon. When using coordination, remember these tips, and you’ll be able to expand your sentences without errors.

Lesson Summary

To review, subordination and coordination are two ways of expanding sentences. Subordination involves adding subordinating clauses using a subordinating conjunction. A subordinating clause is one that begins with a subordinating conjunction. ‘If,’ ‘since,’ ‘because,’ and ‘although’ are all examples of subordinating conjunctions.

Subordinating clauses are incomplete sentences and cannot stand alone. When using subordination, remember to never leave a subordinating clause by itself. If you do so, you will have a fragment. Secondly, always add a comma after the subordinating clause.

For coordination, you are simply adding in information. If you are adding to the subject or verb, remember to use a conjunction. No comma is needed.

For adding two sentences together, you must use one of two methods. First, you can insert a comma and a conjunction. Second, you can insert a semicolon. Do not mistakenly write a comma splice, which is combining two complete sentences using only a comma. This is a major error that must be avoided at all times. If you follow these tips, you’ll be able to make your sentences much more complex and detailed.

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