1. Comma Splice: This occurs when two independent clauses (complete sentences) are joined together only by a comma.
* Example: The dog barked loudly, the mailman ran away.
2. Fused Sentence: This happens when two independent clauses are joined together with no punctuation or conjunction.
* Example: The dog barked loudly the mailman ran away.
3. Missing Conjunction: This occurs when two independent clauses are joined with only a coordinating conjunction (for, and, nor, but, or, yet, so) without a comma.
* Example: The dog barked loudly and the mailman ran away. (Needs a comma before "and")
Important Note: While these are the most common ways run-on sentences are formed, it's important to remember that the primary issue is the lack of proper punctuation and/or conjunction to separate two independent clauses.