A run-on sentence is sometimes called a fused sentence. The concept is simple. If your teacher marks fused sentence or run-on on your paper, it’s because you have put two complete thoughts or independent clauses together without the proper punctuation or any kind of sentence boundary. Here is an example:
It felt like I had a thousand pages to read before submitting my final assignment on Sunday night I managed to turn in my paper at 11:58 pm!
And, here is the corrected sentence:
It felt like I had a thousand pages to read before submitting my final assignment on Sunday night, but I managed to turn in my paper at 11:58 pm!
The key is to remember that you must have some kind of boundary between your independent clauses. You can use punctuation, such as the period or the semicolon, or you can use a comma with a coordinating conjunction (for, and, nor, but, or, so—aka FANBOYS).
