The run-on sentence and comma splice are common punctuation errors that can create confusion in your writing.

Run-on sentence

A run-on sentence occurs when two or more complete sentences (independent clauses) are joined with no punctuation. Here's an example:

Joseph Cornell was an innovative American artist known for his shadow boxes and collages his art became more famous after his death in 1972.

Comma splice

A comma splice occurs when two or more complete sentences are joined only with a comma, which is not strong enough punctuation. This is an example of a comma splice:

Joseph Cornell was an innovative American artist known for his shadow boxes and collages, his art became more famous after his death in 1972.

Five Ways to Fix a Run-on or Comma Splice

Add a period and a capital letter
Add a period and a capital letter to separate the sentences.
- Joseph Cornell was an innovative American artist known for his shadow boxes and collages. His art became more famous after his death in 1972.
Add a comma and a coordinating conjunction
Add a comma and a coordinating conjunction. Coordinating conjunctions are easy to remember as F.A.N.B.O.Y.S.—for, and, nor, but, or, yet, so.
- Joseph Cornell was an innovative American artist known for his shadow boxes and collages, but his art became more famous after his death in 1972.
Add a semicolon
Add a semicolon if the sentences are closely related.
- Joseph Cornell was an innovative American artist known for his shadow boxes and collages; his art became more famous after his death in 1972.
Add a “transitional word”
Add a semicolon and a conjunctive adverb—also known as a “transitional word”. When using a transitional word, the comma should be placed immediately after the transition.
- Joseph Cornell was an innovative American artist known for his shadow boxes and collages; however, his art became more famous after his death in 1972.
- Common Transitional Words:
Add a subordinating conjunction
Add a subordinating conjunction—also known as a “dependent word”—to the beginning or the middle of the sentence.
- Even though Joseph Cornell was an innovative American artist known for his shadow boxes and collages, his artwork became more famous after his death in 1972.
  - In the example above, the comma stays when the conjunction "even though" is added to the beginning of the sentence.
- Joseph Cornell was an innovative American artist because he used objects and items most people would throw away in his work.
  - In this example, the comma is removed when the conjunction "because” is added to the middle of the sentence.
- Common Subordinating Conjunctions:

Source: The Writing Center at Ashford University.