The I-Wish-I-Had-Read-This-Before, Super-Duper, Handy-Dandy Basic Guide for Kicking Run-On Sentences to the Curb
Once you learn the rules, grammar is not hard. Writing is kind of like driving. You can go with your gut/ common sense (this works a lot of the time), and hope that a cop (i.e. professor or GSI) won’t pull you over. Alternatively, you can know for sure where it’s OK to park a comma and where it isn’t. This guide briefly reviews how to pinpoint run-on sentences if you have them.
Step 1: Know the difference between an independent clause and a dependent clause
A clause is a phrase (group of words) that consists of a subject and a verb. It expresses some idea. The most important types of clauses you need to know are independent and dependent clauses.
An independent clause is a group of words that can stand by itself as a sentence. If someone were to read an independent clause out loud, it would sound fine.
Example: The hungry truck driver ate a potato-chip sandwich. The subject is “truck driver,” and the sentence tells us that he ate a potato-chip sandwich.
A dependent clause, however, cannot stand by itself as a sentence. It sounds like it is missing some information. If someone were to read it out loud on its own, we would think, “Why aren’t you going on?” Often, adding some kind of descriptive word to the beginning of an independent clause will turn it into a dependent one:
The following are examples of dependent clauses. The underlined word in each case is the word that turns the independent clause from above into a dependent clause.
After the hungry truck driver ate a potato-chip sandwich (what happened?)
Before the hungry truck driver ate a potato-chip sandwich
Because the hungry truck driver ate a potato-chip sandwich
While the hungry truck driver ate a potato-chip sandwich
But the hungry truck driver ate a potato-chip sandwich
(Note: In case you were wondering, the first four underlined words belong to a class of words called subordinating conjunctions. “But” is a coordinating conjunction—more on that later. These are the official names, just in case you want to name-drop when talking to your English teacher.)
These sentences cannot stand alone. You may think the last one sounds OK, but that’s because in speech sometimes we leave out parts of sentences. That sentence begs the question “What happened?” In order for a dependent clause to be part of a complete sentence, it needs to be placed before or after an independent clause. Each dependent clause gives us more information about the independent clause to which it’s connected.
The dependent clause can be placed either before or after the independent one. For relatively long clauses, a comma can separate the two for clarity:
After the hungry truck driver ate a potato-chip sandwich, he headed to the pub for a nice, cold beer. (example of dependent placed before independent)
The hungry squirrel gnawed on an acorn while the hungry truck driver ate a potato-chip sandwich. (example of independent placed before dependent)
Because the hungry truck driver ate a potato-chip sandwich, he was forced to use the restroom at a nearby gas station just ten minutes later.
Knowing the difference between dependent and independent clauses will also help you avoid sentence fragments.
Step 2: Respect the independence of your independent clauses
Independent clauses are independent; in other words, they need their space from each other. If you jam them together without any punctuation, or, if you separate them with nothing more than measly commas, your GSI will get mad at you, and your paper will start bleeding in red ink.
In general, it is correct to give independent clauses their own periods. This befits their dignity.
I am afraid of squirrels. They are all over campus. (correct!)
I am afraid of squirrels they are all over campus. (not cool)
I am afraid of squirrels, they are all over campus. (also bad)
However, for the purposes of sentence variety and more vivid expression, it is often helpful to combine your dependent clauses into a single sentence.
One easy way is by placing a comma, followed by a coordinating conjunction, between the first and second clauses. Coordinating conjunctions are words like “for,” “and,” “nor,” “but,” “or,” “yet,” and "so" (You can remember the coordinating conjunctions using the mnemonic FANBOYS.) They help tell the story about the relationship between the two clauses.
I am afraid of squirrels, but they are all over campus. I need to get over my phobia as I still have three more years until graduation.
I am afraid of squirrels, for they are all over campus. If they were not all over campus, I would not find them as frightening.
My brother knows I am afraid of squirrels, so he put one in my backpack.
I am afraid of squirrels, and I am also afraid of the nuts that they eat.
If you want to show that two independent clauses are closely linked in meaning (for example, one is the cause of the other), you can also place a semicolon (;) in between them. The semicolon indicates that there is less of a “pause” between the two clauses.
Example: I am afraid of squirrels; they are all over campus.
You can also place a semicolon before the coordinating conjunction in cases where the first independent clause is long and has many commas in it. This helps the clarity, and you can think of the semicolon as a “super comma” in such cases.
I am afraid of squirrels, bunnies, parrots, and chinchillas; but I guess I am just weird.
Step 3: Practice a lot.
You are a smartie, because now you know the basics that will help you avoid run-on sentences FOREVER. Now, show off by doing the following exercises. You can go over them with another smart person just to be sure that you are both really great.
1. Label the following clauses as independent or dependent. Then, change capitalization and punctuation as needed on all of them such that they are complete sentences. For each dependent clause, first underline the word(s) that, if cut out, would cause the dependent clause to turn into an independent clause. Then, add an independent clause to it in order to form a logical, grammatically correct sentence.
I ate a peach
because she is nice
after the storm had passed
roadkill should not be cooked
as time passes quickly
slc tutors are cool
for the bell tolled solemnly
since everyone already knows my name
gradually she learned to type
so sometimes my handouts get a little long
2. First, rewrite the following clauses such that they form a single, grammatically correct sentence. Then, write them such that they form two separate sentences. You may need to delete or add words. Try rewriting the sentences in different ways that are all grammatically correct. Think about how changing coordinating conjunctions and punctuation leads to subtle differences in meaning.
i like singing show tunes they are fun
because there were no more tarts the jack of hearts went home and cried
i brought an umbrella the rain in spain stays mainly in the plain
adolfo is my best friend because he always listens to what i have to say
diane sawyer ate potato chips dipped in ice cream an at home viewer called in to good morning america and told her to do that
Student Learning Center, University of California, Berkeley
©2006 UC Regents