Robin’s blog: Simple rules for fixing run-on sentences

“Run-on sentence!” The phrase conjures up images of teachers armed with red pens and frowns writing in the margins of my school papers.  Sometimes they would simply write “run-on!” and that seemed even worse. In either case, though, what I most dreaded was having to fix them.

It was years before I realized that “run-on” didn’t mean the sentence was too long. It meant the sentence was not built right.  The often accompanying phrase “comma splice” helped me see this more precisely.  It turns out that a run-on sentence is two or more sentences melded incorrectly into one.

Over the years, like many others, I have learned to write acceptably while often not really knowing the rules, and that’s one way to proceed. But everyone approaches writing in their own way, and it often helps to understand the basics if you want to find and fix errors.

Doing some research now, I’m not surprised that run-ons confused me.  There are actually two kinds of run-ons, one where the sentences are just mushed together with no punctuation, the other where they are joined by a comma. The latter is the infamous “comma splice” (and just to confuse things, there are a few rare cases where a comma splice is OK).

Is it a run-on?  First find the subject and verb

I’m not big on mastering grammar skills just for the heck of it. But any time your writing  isn’t communicating well enough, you may have to face learning some grammar. The subject and verb are the core of sentence structure – and usually should be meaning-wise as well.

For some people this skill needs no review, but for others it just never quite clicks, quite a bit like me and freshman algebra.  Either way, though, it’s a skill that can be improved with practice (and if you learn to approach your writing analytically using this kind of tool, you might find yourself actually enjoying it).

So, to find subject and verb, two basic questions to ask when you confront a sentence:

1.  What’s happening?

2.  Who’s doing it?

Of course, just to keep it tricky, you have to include “is,” “was,” “are,” “were” and all the other forms of the verb “to be” in the category of “doing,” as often one of those forms of “to be” will be your primary verb.

And we must not forget the imperative verbs, as in the sentence “Go to the door.” There the verb (the only word there that’s an action) is “Go,” and the person “doing” the action is “you.”  Another way to say it is “You! Go to the door!” See the implicit “you” as the subject in the three-word form?

Concentrate on finding the “center” of the sentence. Sometimes it won’t exactly match the “center” in terms of the sentence’s meaning. Remember you’re looking at the sentence’s structure: that is, how the words fit together and relate to one another.

First type of run-on:  The mushed-together sentence

If your sentence has more than one subject-and-verb pair, you should stop to make sure it’s not a run-on. For example, “We saw him he ran out the door.” Because you have two subjects (we and he) and two verbs (saw and ran), you need to separate them somehow.  Two ways to do this:

1.  With punctuation

2.  With more words that explain how the two are related

The easiest fix here:  Separate this into two sentences, with a period after “him.” To convey a closer relationship between the parts, you can instead use a semicolon (;) between them. Semicolons can be tricky, though, and you won’t go wrong if you simply make two sentences.

Second type of run-on:  The comma splice

To understand the comma splice, imagine the example above with its parts separated by nothing more than a comma after “him”:

“We saw him, he ran out the door.” 

That’s a comma splice, and these are almost never OK (see below for exception). You’re trying to join two sentences with a weak little comma.  It doesn’t sound really bad, but it’s not acceptable in most kinds of formal writing. You can fix this sentence as we did above by:

1. Making two sentences or

2. Using a semicolon between the two parts

Sometimes you can convey more meaning by linking the two parts with an additional word:

“We saw him but he ran out the door.” Or

We saw him because he ran out the door.

The first example uses but, a coordinating conjunction; the second uses because, a subordinating conjunction.

And yes, that’s jargon.  But it’s worth understanding:

A coordinating conjunction is a word like “and” or “but” that  is used to join two parts that could each stand alone.

A subordinating conjunction is a word like “because” or “when.” In joining the two parts, it makes one “subordinate” to the other, turning it into what’s called a dependent clause. You are making one part of your sentence dependent on the other part to make complete sentence.

The comma before a coordinating conjunction (“and,” “but,” etc.) is optional though it’s often useful, especially if the parts are long. With a subordinating conjunction (“because,” “when”) using a comma is wrong because the second part is dependent on the first. Using a comma signifies you could separate them to stand alone (and to carry this further, you can begin a new sentence with “And” or “But” if you really want to). But using a word like “because” creates a sentence where both parts are required to convey the sentence’s meaning, so no comma.

When the comma splice is OK:  I came, I saw, I conquered

There are a few times in which a “comma splice” is appropriate. I always think of the example “I came, I saw, I conquered.” In each part “I” is the subject and the three verbs also are pretty obvious. The commas are OK essentially because the parts are short. It’s a nice construction, but there’s not much point in risking it unless you really want to. (The quote is from the Roman emperor Julius Caesar, whose desire to express himself that way not many would have questioned, as he had a way of acting well described in the phrase itself.)

Examples of run-ons and fixes:

WRONG: “We saw him he ran out the door.”

WRONG (99% of the time): “We saw him, he ran out the door.”


“We saw him. He ran out the door.”

“We saw him; he ran out the door.”

“We saw him but he ran out the door.”

“We saw him because he ran out the door.”

What could be easier? Surely not freshman algebra!

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