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University Writing Center

Sentence Sense

Run Togethers, Comma Splices, and When to Use Semi-Colons

When you began reading, your books were written in very simple sentences. Then you began to write, and of course, you began with simple sentences. If you can write complete sentences, you’re fine (and safe) writing simple sentences. But most people want to combine sentences for variety and style.

You can write two sentences:

My brother graduates from college this month.

He will enter med school soon.

But you shouldn’t just join these two sentences into one:

My brother graduates from college this month he will enter med school soon.

This error is called a “run-together.”

You also shouldn’t join the two sentences with only one comma:

My brother graduates from college this month, he will enter med school soon.

This error is called a “comma splice.”

You have three ways that you can join two sentences:

  1. a semi-colon
  2. a comma plus one of the coordinating conjunctions — and/but/or.
  3. rewriting one sentence so it is a dependent clause (followed by a comma).

Using a semi- colon:

My brother graduates from college this month; he will enter med school soon.

Using a comma plus a coordinating conjunction:

My brother graduates from college this month, but he will be going to med school soon.

Rewriting one sentence so that it is dependent on the other sentence:

After my brother graduates from college, he will enter med school.

Caution: Do not use a semi-colon between a dependent clause and a sentence (independent clause). A good test for whether a semi-colon can be used is to ask if a period can be used instead. If so, the semicolon is correct.

A review of correct ways to join sentences:

  • Sentence. Sentence.
  • Sentence; sentence.
  • Sentence, conjunction (and/but/or) sentence.
  • Dependent clause, sentence.

If you need more information about joining sentences, please ask.

Updated 1.13.2012