Run-ons/Comma Splices

A run-on sentence, a common mistake of writers, occurs when you put two ideas together with no punctuation between them or only a comma. Here’s a run-on example: 
  • A car can also show your personality you show you’re economical.

In this example, the first part, “A car can also show your personality,” is a complete idea. The second idea begins with “You show,” which expresses a new subject and a new verb.

A comma splice is a special kind of run-on where there is a comma either where there shouldn’t be one, or where stronger punctuation is needed. Here’s a comma splice example:

  • A car can also show your personality, you show you’re economical.

Every run-on sentence calls for its own correction. Most of the time, you will add punctuation and a connecting word. Sometimes, though, you would do better if you rewrote the sentence to make a shorter sentence with only one main idea. Below are some standard methods for correcting run-ons. As you apply these concepts, be sure to check to see if both ideas are complete ideas, also known as independent clauses. Does each idea have its own subject and complete verb? Can each idea stand alone as a sentence?

Here are six ways to fix a run-on:

Find the point where the two ideas join. Put a period. Make two simple sentences.

  • A car can also show your personality. You show you’re economical.

Combine the two ideas into one simple sentence by making one of the ideas into a phrase or adjective or adverb.

  • A car can also show your economical personality.

Find the place where the ideas join and put a comma plus a coordinating conjunction. These conjunctions are connecting words used in compound sentences.

, and , for
, but , yet
, so neither, nor
, or either, or
  • A car can also show your personality, and you show you’re economical.

Find the place where the ideas join and put a semi-colon (;) and an “adverbial conjunction.” These conjunctions are connecting words used in compound sentences:

; however, ; then, ; furthermore,
; thus, ; moreover, ; also,
; for example, ; as a result, ; consequently,
; nevertheless,    
  • A car can also show your personality; for example,  you show you’re economical.

Find the place where the ideas join and put a semi-colon. Do this only if the second idea is closely related to the first idea; for example, the second idea might be a more specific version of the first idea.

  • A car can also show your personality; you show you’re economical.

Find the place where the ideas join and put a subordinating conjunction. These conjunctions are connecting words used in complex sentences. If they are placed between the two ideas, no punctuation is needed.

when after unless because who
before while although since which
since when even though   that
as until if    
  • A car can also show your personality because you show you’re economical.
  • Since a car can also show your personality, you show you’re economical.

Taken from: http://owl.ccd.edu/writ_resources/handouts/RunOn_Exp.html