A run-on sentence is a common error caused by merging two sentences without suitable punctuation. The most common run-on sentence is the "comma splice" (also known as the "comma fault"), which occurs when two sentences are inappropriately separated by a comma.
1 Divide the clauses into two sentences
Often in writing, the best way to fix a run-on sentence is to split it into two or more separate sentences. Be sure to capitalize the first letter of each sentence and use a period,
question mark, or exclamation point between them.
2 Insert a semicolon between the two clauses
Another way to write better sentences is by using a semicolon to connect two clauses in the same sentence. This works great for comma splices because you can simply replace the
comma with a semicolon.
3 Use a comma and a conjunction
Conjunctions work well for describing the relationship between two clauses. You can use either a coordinating conjunction (for, and, nor, but, or, yet, and so) or a subordinating
conjunction (because, if, while, etc.).
If you use a coordinating conjunction, place a comma before the conjunction. If you’re using a subordinating conjunction, use a comma only if the subordinate clause comes first.
You don’t need a comma if the subordinate clause comes second.