If you have glanced through the Writing Center s resources, you can see that there are a lot of things to know about grammar, and a lot of mistakes that students can make with grammar. However, the most common mistakes students make are ones involving sentence structure: run-on sentences, comma splices, and sentence fragments. So this tutorial has a lot of information but that s because it is all so important! This is all about knowing when to stop a sentence just like you end a race at the finish line, you don t want the sentence to keep running on after the finish line or to stop short of that finish line. Sentence Basics A few definitions will help: Subject = a doer in the sentence, the person or thing doing something Verb = the action in a sentence Clause = a group of words with a subject and verb Independent clause = a clause than can stand on its own as a simple sentence Dependent clause = a clause that has a subordinating conjunction (a type of joining word) added, so it can t stand along it need to be attached to another independent clause. This is all important because a sentence is the most basic form of language. A sentence needs to express an idea and communicating ideas is why we developed language in the first place! (You can also read about these ideas in our tutorial on Sentence Structure) You need two things to have a complete sentence: a subject (a doer) and a verb (the doer s action). It also needs to express a complete thought. Check out this example: Ann loves to braid her long hair. She wears it like that daily. We can see here that there are two complete sentences (also called independent clauses ); the first subject is Ann and the verb is loves. The second sentence has a pronoun subject of she and a verb of wears. Every complete sentence should have a clearly connected pair of a subject and verb in each construction. Most importantly, each of these sentences expresses a complete thought. Run-On Sentences and Comma Splices These two mistakes are basically the same thing. This is where you have joined two (or more) sentences together improperly, or run them together.
If we rewrote our two original sentences as a single sentence without punctuation, it would be considered a fused or run-on sentence, like this: Ann loves to braid her long hair she wears it like that daily. Notice that one subject-verb idea runs right into the next without anything to connect them properly or separate the ideas. Often this happens we writers get on a roll and forget to stop and make ideas separate and clear from the reader. Also, these mistakes often happen when the second idea starts with a pronoun that refers back to a noun in the first idea (notice she in this example refers to Ann from the first idea). In the writer s mind, since it is the same subject, it becomes one idea. But a pronoun is still a new subject, and if that subject does something new, you have a new idea. Often, people think you can fix this issue by putting a comma between the two thoughts: Ann loves to braid her long hair, she wears it like that daily. But this comma has not fixed anything it has just created what we call a comma splice. A comma is not strong enough punctuation to separate two complete thoughts (two complete sentences). Luckily, there are 4 ways to fix run-ons and comma splices: Option 1: Change the comma (in the case of a comma splice) with a semi-colon (please check out our tutorial on Commas and Semicolons), or if it is a run-on, put the semi-colon between the two ideas: Ann loves to braid her long hair; she wears it like that daily. Option 2: Change the comma (in the case of a comma splice) with a period, or if it is a run-on, put the period between the two ideas (notice that the first letter of the second sentence needs to be capitalized, since it is a totally new sentence now): Ann loves to braid her long hair. She wears it like that daily. Option 3: Join the two sentences together with a comma plus a coordinating conjunction. There are only 7 coordinating conjunctions (for, and, nor, but, or, yet, so they are easy to remember since if you take the first letter from each, it spells FAN BOYS). Ann loves to braid her long hair, and she wears it like that daily. Note: Please be careful here not to let transitional words like however or otherwise get confused with coordinating conjunctions. You can use transitional words, but they cannot simply be used with a comma to connect ideas like coordinating conjunctions can. Why can only the coordinating conjunctions (the FAN BOYS ) be used this way? As with all English grammar, rules develop organically from the way we use ideas in order to best communicate them to each other. This is just one of those rules. See the disclaimer at the end of this tutorial about all of the weirdness of grammar rules!
Option 4: Join the two sentences together by adding a subordinating conjunction and making one sentence dependent (called a dependent clause ) on the other one. There are quite a few subordinating conjunctions, but some common ones are: after although as as if because before during even though if In order to once since so that though unless until whatever when whenever whether Notice that if we add one of these words to the beginning of a simple sentence, it can no longer stand alone, since it no longer expresses a complete thought: Since Ann loves to braid her long hair. If we left the sentence like this, it would be a sentence fragment (see below for explanation of that mistake) since it does not express a complete idea. But adding the subordinating conjunction allows us to attach this idea correctly to another complete sentence: Since Ann loves to braid her long hair, she wears it like that daily. We could also add the subordinating conjunction at the beginning of the second sentence, which would put it between the two sentences: Ann must love to braid her long hair because she wears it like that daily. Which of these four ways should you choose? Well, all of them make the sentence correct, but which you choose comes down to style which you think sounds and looks best as part of your paper. In general, sentence variety (some short and simple, some longer and complex, some combined with coordinating conjunctions, etc.) makes for a more interesting tone to your paper, so mix it up! You can also read about how to combine sentences in our tutorial, Combining Sentences. Fragments Fragments are sort of the opposite problem of run-ons and comma splices. Instead of letting the sentence go on too long, a fragment does not express a complete though before stopping. Fragments therefore are incomplete sentences. They cannot stand on their own. Here are some examples: While he was sleeping. Anthony put the book.
As you were reading these, you probably thought, While he was sleeping WHAT? and Anthony put the book WHERE? These examples are incomplete sentences because they do not finish their thoughts. It may seem like there is a doer (subject) and action (verb), but there is something either added or missing that keeps each of these examples from expressing a complete thought. In the case of the first incomplete sentence example above, which is the most common fragment type, our fragment is a dependent clause. This means it needs another clause, an independent clause (otherwise known as a complete sentence), to depend on. Please review these ideas above in the run-ons section again if they are confusing. You will usually find the independent clause next to your fragment, so all you need to do is join them: Incorrect: While he was sleeping. His mother called. Correct: While he was sleeping, his mother called. In the case of the second incomplete sentence, we are just missing a few words. These types of fragments usually result from something being revised and not proofread. Incorrect: Anthony put the book. Correct: Anthony put the book down. Correct: Anthony put the book on the bookshelf. Correct: Anthony put the book under the sofa where no one else could find it. A sentence can be quite long and still not be complete. Remember that you need a matching subject and a verb combination to make a sentence, and it must express a complete thought. The following examples may seem long enough, but can you see what they are missing to make them fragments? Running all alone at night, surrounded by a pack of wild dogs in the moonlight. My uncle, a big man who always seemed to always have the right thing to say. In the first example, we do not know who or what is running, so we are missing a subject. In the second example, we have a subject my uncle, but he is not doing anything, so we are missing a verb to go with our subject (there may be other verbs in the sentence, but if they do not match with the subject, the thought is not complete). Also watch out for clauses starting with who, which, or that. These are types of pronouns (something standing in place of a noun) that can t stand alone as subjects of a sentence. They would have to refer back to a noun in the first part of a sentence. Notice how the second part of this example is a fragment: I need the shovel. Which is in the garage. This is easily fixed by simply taking out the period and connecting the two ideas: I need the shovel, which is in the garage.
Grammar Rules Disclaimer Okay so you know it all by heart, right? And now you re set for life, right? Well unfortunately, grammar rules do change over time, as our language develops. This takes a long time, so the rules we provide for you are current now, but keep in mind that years in the future, when your greatgrandchildren tell you they learned these rules a different way, they may not be wrong by then! Test Yourself! Correcting sentence structure errors can be a long, difficult journey and takes practice. To test how well you understand these ideas, please try out our practice test, located in the Writing Mechanics Section of the Writing Reference Library. Then check out your own papers to see where you may find mistakes of your own, since now you know how to correct them. Just remember that writing skills like these take a lot of time and patience to master in the study of writing, it is all about the journey, not the finish line!