A run-on (or fused) sentence is when two or more sentences are written without punctuation dividing them. A comma splice is when two sentences are divided by a comma. Both a run-on and comma splice are incorrect English grammar.
Run-on: The grass was tall I cut it.
Comma splice: The grass was tall, I cut it.
Run-on and comma splice sentences can be fixed in several ways.
1. A period .
The grass was tall. I cut it.
2. A semi-colon ;
The grass was tall; I cut it.
3. A coordinating conjunction [, + for and nor but or yet so] The grass was tall, so I cut it.
4. A conjunctive adverb [; conjunctive adverb,] or [. conjunctive adverb,]
The grass was tall; therefore, I cut it.
5. A subordinating conjunction
Because the grass was tall, I cut it. (showing reason)
The grass was tall before I cut it. (showing sequence)
If the subordinating conjunction begins the sentence, there should be a comma after the dependent clause; however, a comma is not necessary if the subordinating conjunction is in the middle of the sentence. Notice the difference between the two examples above.
Exercise 8-Identifying Run-ons and Comma Splices
Identify whether the sentence is a run-on or comma splice. Correct the sentences using one of the five strategies above.
____ 1. Yasmeen had been planning this trip for months; however, when her work called she couldn’t say no.
____ 2. Ammar had enjoyed the trip he saw so many new places.
____ 3. Chen turned off the lights, he forgot to lock the door.
____ 4. Jose did not work today, however, he did not relax.
____ 5. Once Onika got home she began studying for her exam.
"Grammar Presentation Run-Ons and Comma Splices" in Advanced Academic Grammar for ESL Students by Rebecca Al Haider is licensed under a CC BY 4.0 license. Adapted by Laura Paciorek.