|Once you have written a sentence, do not be tempted to put a comma and write another sentence. This is the most common mistake involving commas. It is called a run-on error.|
What Is a Sentence?A sentence is a grammatically complete series of words. A sentence must have a subject and a verb, even if one or the other is implied, and express a complete concept. A sentence begins with a capital letter and normally ends with a full stop (period ).
(NB: A sentence can also end in a question mark (?) or an exclamation mark (!). If we're being really pedantic, it could also end in a speech mark, but it definitely can't end in a comma.)
Run-on ErrorOnce you have formed a sentence (i.e., expressed a complete concept), you must put a full stop (or period ) or another valid ending (like ! or ?) and end the sentence. Do not insert a comma and continue writing. This is a very common mistake. It is known as a run-on error, a run-on comma, or a run-on sentence. For example:
Pick up a copy of our free brochure, this explains how to contact us and reach our
(This is two sentences. You cannot put a comma after brochure and carry on writing.)
Everyone is aware of the road works in the village, we are still here, come and visit us.
(This is three sentences. You cannot put a comma (after village and here in this case) and carry on writing.)
Your Idea Could Consist of Several Sentences
often feel that a comma is more appropriate than a full stop (or period ) because their sentences are so closely related. In other words, they sense that a full stop
(or period )
is too abrupt, because they haven't finished expressing their idea.
This is at the root of this error. Remember, a sentence is a grammatically complete series of words. Often, it will take several sentences to complete your idea. Look at the examples below:
ALTERNATIVES TO A COMMA
Occasionally, it may be appropriate to use a dash or a semicolon instead of a full stop. See the lesson Extend a Sentence.