Combining Clauses to Avoid Comma Splices, Run-ons, and Fragments

*The data are inconclusive the researchers will repeat their experiment.

*The data are inconclusive, the researchers will repeat the experiment.

*Since the data are inconclusive.

In academic writing, we often combine clauses to express complex ideas within one sentence. We can link clauses with conjunctives, or words that illustrate the meaning between two clauses. If these words and punctuation marks are used incorrectly, sentence structure problems can occur, as illustrated in the three examples above. In this handout, you will learn about different ways of combining clauses, and how to avoid comma splice, run-on, and fragment mistakes.  


A clause is defined as a word grouping that contains a subject and a verb. There are two kinds of clauses: independent clauses, which convey complete meaning and can stand alone as simple sentences, and dependent clauses, which do not express a complete idea on their own and must be paired with another clause. We use different conjunctive words and punctuation to connect these different types of clauses.

Structuring Sentences with Independent Clauses

OPTION 1:Use a comma and a coordinating conjunction


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Example: The article was published in a peer-reviewed journal, so it is a credible source.

OPTION 2: Use a semicolon

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Example: The article was published in a peer-reviewed journal; it is a credible source.

OPTION 3: Use a semicolon, transition word, and comma

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Example: The article was published in a peer-reviewed journal; therefore, it is a credible source.

We structure coordinating clauses in these ways to avoid creating run-on sentences and comma splices.

A run-on sentence is a mistake that occurs when two independent clauses are combined without using any conjunctive words or punctuation marks. Our first example sentence at the beginning of the handout (The data are inconclusive the researchers will repeat their experiment) illustrates this problem. It is difficult to distinguish the two ideas, and the reader might be confused about the meaning of the sentence.

A comma splice mistake can be seen in our second example (The data are inconclusive, the researchers will repeat the experiment). It incorrectly joins two clauses with a comma only. To form a grammatically correct sentence, a comma should be followed by a coordinating conjunction or changed into a semi-colon.


Structuring Sentences with Dependent Clauses

OPTION 1: Use a subordinating conjunction after the independent clause

Note: there is no punctuation before a subordinating conjunction when the subordinating conjunction is in the middle of the sentence.

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Example: The chapter is dense because it is thorough.

OPTION 2: Start sentence with the subordinating conjunction and add a comma after the dependent clause

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Example: Because it is thorough, the chapter is dense.

A fragment, as our third example shows (Since the data are inconclusive), is an incomplete sentence. Oftentimes, fragments occur when dependent clauses are not connected to an independent clause, but left to stand alone. (Learn more about fragments from the handout “Avoiding Fragments with Dependent Clauses”)

Information in this handout is adapted from Fawcett, S. (2007). Evergreen: A guide to writing (8th ed.). Houghton Mifflin Company.


- Check to see if your sentence has only one subject-verb combination. If there are two (or more) combinations like that, then there are two separate clauses in the sentence, and they need to be combined using one of the above methods.

- Identify fragments by looking at the first word of the sentence. If it starts with a subordinating conjunction, such as since, while, which, who, or until, it needs to be connected with another clause. Look at the sentence directly after the fragment and see if the ideas of each clause are related and use Option 2 from the Structuring Sentences with Dependent Clauses section from this handout to turn the fragment into a full sentence.


In the passage below, identify and correct any errors related to combining clauses.

The instructor uses behaviorism, constructivism, and the information processing theory successfully in her classroom on a daily basis however, one theory that she uses in correlation to all these theories is the Sociocultural Theory. It is important for students to learn from constructing their own portfolios they learn to write about situations and cultures within their own framework. The combination of the two methods not only allows students to understand new information in association with the information they already know. They also get practice constructing the new information within their own schemas. The best method for a classroom with a diverse group of students is to vary the different learning theories, it is important to continue to anticipate problems and solutions in order to help the students learn best in their own ways. To individualize the learning process, the instructor must evaluate the needs of each student for example some students maybe be auditory learners while others process information visually. Although individualization is effective. This mode of teaching requires the instructor to devote more time to planning and customizing classroom lessons. The instructor may need extended planning time, a teaching assistant can provide additional support in this case.

Practice exercise adapted from Michigan Corpus of Upper-level Student Papers. (2009). Ann Arbor, MI: The Regents of the University of Michigan.                                                                                                                                                                         
Last updated11/16/2017