Constructing Sentences - Run Ons and Fragments

Even if English is your native language, it is still easy to make these common sentence structure errors. Transferring our spoken ideas to paper can be a challenge to determine where and how ideas should be separated by punctuation marks.

The two main errors are run-on sentences and sentence fragments. Take a look at the quick description of the two types of sentence errors below. For more detailed explanation of the kinds of possible sentence errors, click on the tabs to the left. 

1. Run-on sentences

When we speak, we often run sentences together, but our tone and pauses help people understand what we are saying. In writing, however, we rely on standard punctuation to help us read more easily. If you write two or more sentences together as if they were one sentence, you have created a “run-on.” There are two types of run-on sentences: fused sentences and comma splices. 

The following statements would cause no problems in speech, but if they are not punctuated properly in writing, the reader may be confused for at least a moment. 

Example incorrect sentences:

Mary ate the dog watched. (fused sentence)

• I could not find it, every day I looked for it again. (comma splice)

Mary ate. The dog watched.

• I could not find it. Every day I looked for it again.

Note: In some cases the subject or verb is considered to be “understood” rather than actually written.  

• For example: “Close the door.

​The subject is considered to be the person to whom the request is directed. This sentence is in command form. In academic writing, the subject and verb are almost always written.

2. Sentence fragments

Whereas a "run-on" can be seen as a sentence containing too many complete thoughts without the proper punctuation or connectors, sentence fragments have the opposite problem. They may have a missing subject or verb or maybe an incomplete thought.

Example Incorrect sentences:

• After the concert.
• And ate the whole thing.
• Including me.
• Hanging out with friends.
• Looking for a new dress.
• Covered in dirt.
• To go to Spain.

The sentences above can be rewritten as:

• After the concert, I went straight home.
• My brother bought a cake and ate the whole thing.
• Everyone went to the concert, including me.
• I love hanging out with friends.
• She's at the mall looking for a new dress.
• He came home covered in dirt.
• I'm saving up to go to Spain.

Fused sentences

This type of run-on occurs when the writer combines two or mores sentences together without joining words or the necessary punctuation.

Examples of fused sentences:

• Edward left early he was sick.
• There are many factors contributing to the recent decline in the per capita rate of smokers one important influence has been the targeting of teenage girls with anti-smoking posters and radio ads.

Both of these sentences have two sentences that are combined as single sentences without any joining words or punctuation. Let's break these sentences down so that the separate sentences are easier to see.

Example 1:

It is clear that these two complete thoughts are related, but they require a semi-colon or a connector to make the sentence correct.

Here are a few ways the fused sentences can be rewritten:

1. Edward left early; he was sick.
2. Edward was sick, so he went home.
3. Because Edward was sick, he went home.
4. Ed left early. He was sick.
5. Edward was sick; therefore, he went home.

Example 2:

This fused sentence is quite long, which makes it even more difficult for readers to understand it.

Here are a few ways the fused sentences can be rewritten:

1. There are many factors contributing to the recent decline in the per capita rate of smokers. One important influence has been the targeting of teenage girls with anti-smoking posters and radio ads.
2. There are many factors contributing to the recent decline in the per capita rate of smokers. For example, one important influence has been the targeting of teenage girls with anti-smoking posters and radio ads.
3. There are many factors contributing to the recent decline in the per capita rate of smokers; one important influence has been the targeting of teenage girls with anti-smoking posters and radio ads.

Comma splices

This type of run-on occurs when the writer tries to hold sentences together with a comma.  Just adding a comma won’t fix a fused sentence.  A comma is considered too “weak” to hold sentences together.

Examples of comma splices:

1. I was late, I slept in.
2. There are many ways in which people try to find a job, some people go to a job search agency.

Both of these sentences contain 2 complete thoughts each and are clearly related to each other, but they require punctuation, or a connector to make the sentences correct. 

Example 1: I was late, I slept in.

Here are a few ways the sentences can be written:

• I was late. I slept in.
• I slept in, so I was late
• Because I slept in, I was late.
• I was late; I slept in.
• I slept in; therefore, I was late.

Example 2: There are many ways in which people try to find a job, some people go to a job search agency.

Here are a few ways the sentences can be written:

1. There are many ways in which people try to find a job. Some people go to a job search agency.
2. There are many ways in which people try to find a job. For example, some people go to a job search agency.
3. There are many ways in which people try to find a job; some people go to a job search agency.

Missing subject

Sometimes fragments are missing subjects and therefore incomplete. The missing subject may be the same as the previous sentence. The sentence fragments below can be corrected by adding subjects.

Examples:

• Was just at the bank.
• Went to the post office.

The fragments can be corrected as follows:

• I was just at the bank.
• I went to the post office.

Incomplete thought

Sentences may include a subject and a verb, but they can still be incomplete. These kind of fragments can sound natural because we use them all the time in natural conversation. When we write, especially academically, they are considered sentence fragments. Go through the following list of common incomplete sentence types to improve your editing skills.

1) No main clause

a) Starting with a subordinator

Many sentence fragments start with a subordinator, but lack an independent clause. Subordinate clauses (or dependent clauses) can't stand alone, which make them incomplete thoughts. 

Your sentence may be a fragment if it begins with one of the following subordinators:

Note: See the connectors guide for more information.

Examples:

The bold phrases are the sentence fragments.

• While I was sleeping. The phone rang.
• Before I went to school. I checked the weather report.
• Although I didn't study for the test. I still passed.

Here are some possible ways to complete these thoughts:

• While I was sleeping, the phone rang.
• Before I went to school, I checked the weather report.
• Although I didn't study for the test, I still passed.

b) Extra detail or afterthoughts

Because many people write how they speak, this is a very common sentence fragment. When there is no main clause, the group of words is considered a fragment.

Your sentence may be a fragment if it begins with one of the following words/phrases:

Examples:

• I didn't tell anyone about the accident. Including my best friend.
• I did many things on my vacation. For example, skiing, snowboarding, and snowshoeing.
• We were all very tired. Especially my brother.

Here are some possible ways to correct the fragments above:

• I didn't tell anyone about the accident, including my best friend.
• I did many things on my vacation, for example, skiing, snowboarding, and snowshoeing.
• We were all very tired, especially my brother.

2) Phrase that is not modifying anything

a) Phrase starting with a coordinate conjunction

Sentence fragments starting with a coordinate conjunction (FANBOYS - for, and, nor, but, or, yet, so) are probably the most common. Students often get confused about whether they are allowed or not in academic writing because they appear so often in books and other written material. If you are writing formally, or you are an inexperienced writer, it is better to avoid making this kind of fragment. (See to the connectors tab for more information.)

Examples: 

• She came to my wedding. But she was wearing jeans!
• I was not happy. Nor was my husband-to-be.
• I was tired. So I went to bed early.

The above phrases can be combined to make sentences:

• She came to my wedding, but she was wearing jeans!
• I was not happy, nor was my husband-to-be.
• I was tired, so I went to bed.

b) Starting with a participial phrase

What is a participle? A participle is a word formed from a verb. There are past participles and present participles. Present participles end in "ing". Regular past participles end in "ed". Irregular past participles can end in "n", "t", or "d". A participial phrase is a group of words that starts with a participle. Although participles look like verbs, they behave as adjectives when they are in a phrase. 

Examples:

• I was at the mall all day. Looking for a new bag.
• I drove down the highway. Covered in snow.
• I saw her. Burst into tears.
• I helped a dog. Bitten by a coyote.

The above phrases can be combined to make sentences:

• I was at the mall all day looking for a new bag.
• I drove down the highway covered in snow.
• I saw her burst into tears.
• I helped a dog bitten by a coyote.

c) Starting with a "to" verb

An infinitive phrase starts with the infinitive form of the verb ("to").  When a group of words start with "to", it sometimes becomes a fragment. Infinitive phrases look like verbs, but they behave as nouns, adjectives, or adverbs. For sentence fragments, infinitive phrases are usually adverbs that are not describing anything. They need a subject and verb to form a complete sentence. 

Examples:

• I called my friend. To ask her if she wants to go shopping.
• I tried really hard. To finish my project on time.
• My boss sent out an email. To announce his retirement.

The above phrases can be combined to make sentences:

• I called my friend to ask her if she wants to go shopping.
• I tried really hard to finish my project on time.
• My boss sent out an email to announce his retirement.

There are five main ways to correct run-on sentences. Take a look at the run-on sentence below:

• He decided to run a marathon he wanted to challenge himself.

Read through the five ways to correct run-on sentences to see how the sentence above can be corrected.

Method 1: 

Break the complete thoughts into separate sentences.

Example: He decided to run a marathon. He wanted to challenge himself.

Method 2:

Use a coordinating conjunction and a comma.

Example: He wanted to challenge himself, so he decided to run a marathon. 

Note: If both sentences are short, the comma may be omitted. Mary ate and the dog watched. But it’s safer to use both the joining word and the comma. 

​Method 3:

Use a subordinating conjunction to make one idea dependent on the other.

Examples:

• He decided to run a marathon because he wanted to challenge himself.
• Because he wanted to challenge himself, he decided to run a marathon.

Note, if the joining word appears at the beginning of the first sentence, a comma is needed before the second sentence.  If the subordinating conjunction is in between the sentences, no comma is needed.

Method 4: 

Use a conjunctive adverb.

Example: He wanted to challenge himself. Therefore, he decided to run a marathon.

Method 5: 

Use a semi-colon (and a conjunctive adverb)

Examples: 

• He decided to run a marathon; he wanted to challenge himself.
• He wanted to challenge himself; therefore, he decided to run a marathon.

Exercise: Correct these sentences using the five methods. 

1. I told him not to do it he did it anyway.
2. I didn't study I still passed.
3. The weather was so beautiful we stayed outside all day.

Reveal answers

There are two main ways to correct sentence fragments. Take a look at the sentence fragments below: 

• She ate the whole pizza. Can't believe it!
• Go to the beach every day! I love it. 

Read through the two ways to correct sentence fragments to see how the sentence above can be corrected. 

Method 1:

Attach the fragment to the sentence before or after it. 

Examples: 

• I can't believe she ate the whole pizza!
• I love going to the beach!

Method 2:

Attach a subject or verb to the fragment. 

Examples:

• She ate the whole pizza. I can't believe it!
• I go to the beach every day. I love it!

Exercise: Correct these fragments using the one or both of the methods above. 

1. I couldn't reach you. Been trying to get you on the phone for hours!
2. Do you know who came? My old friend from high school.
3. I saw her! Before class.
4. I want a new car. Like yours!
5. I saw him. Crying over the death of his pet.
6. She rushed into the office. Drenched in sweat.
7. Singing with my friends.
8. I want to see her. To talk to her once more.
9. I went to my ex-boyfriend's wedding. But I didn't want to.

Reveal answer