Run-on Sentences
A run-on sentence occurs when two or more independent clauses are joined without proper punctuation or connecting words. This is one of the most common writing errors, and it comes in two main forms.
Types of Run-on Sentences
A comma splice joins two independent clauses with only a comma, without a coordinating conjunction:
I love coffee, I drink it every morning.
A fused sentence (also called a run-on in the strictest sense) smashes two independent clauses together with no punctuation at all:
I love coffee I drink it every morning.
Both are errors because each clause is an independent clause, meaning it has a subject, a verb, and expresses a complete thought. Independent clauses can't just be glued together without the right punctuation or connecting word.
Identifying and Correcting Run-on Sentences
To spot a run-on, look for places where two subject-verb pairs appear without proper separation. Once you find one, you have several ways to fix it:
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Split into two sentences. Use a period.
- I love coffee. I drink it every morning.
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Add a comma + coordinating conjunction. The coordinating conjunctions are FANBOYS: for, and, nor, but, or, yet, so.
- I love coffee, and I drink it every morning.
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Use a semicolon. This works when the two clauses are closely related.
- She's an excellent writer; her novels are bestsellers.
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Use a semicolon + conjunctive adverb. Words like however, therefore, moreover, and consequently can clarify the relationship between clauses. Place a semicolon before the adverb and a comma after it.
- I'm tired; therefore, I need to sleep.
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Make one clause dependent. Add a subordinating conjunction (because, although, when, if) to turn one clause into a dependent clause.
- Because I'm tired, I need to sleep.
Common Mistakes and Prevention
- A long sentence is not automatically a run-on. Length doesn't determine correctness. A properly punctuated sentence can be quite long and still be grammatically sound.
- A compound predicate (two verbs sharing one subject) does not need a comma: She sang and danced.
- Watch for subtle run-ons in dialogue or informal writing: He said he was coming I don't believe him is a fused sentence.
- Practice finding subject-verb pairs. If you can identify two independent clauses, check that they're connected properly.
Sentence Fragments
A sentence fragment is a group of words that looks like a sentence but is missing something essential: a subject, a verb, or a complete thought. Fragments leave the reader hanging because they don't express a full idea.
Types of Sentence Fragments
Each type is missing something different:
- Missing a subject (no one is doing the action): Went to the store.
- Missing a verb (no action or state of being): The cat on the windowsill.
- Dependent clause standing alone (has a subject and verb but starts with a subordinating conjunction, so it can't stand on its own): Because it was raining.
- Participle phrase (a verb form like -ing or -ed used without a main clause): Running through the park.
- Infinitive phrase (starts with to + base verb, without a main clause): To finish the project on time.
Correcting Sentence Fragments
The fix depends on what's missing:
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Add a subject to fragments that lack one.
- Fragment: Went to the store. → Fixed: She went to the store.
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Add a verb to fragments missing an action or state of being.
- Fragment: The cat on the windowsill. → Fixed: The cat sat on the windowsill.
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Attach dependent clauses to an independent clause.
- Fragment: Because it was raining. → Fixed: Because it was raining, we stayed indoors.
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Connect participle phrases to a complete sentence.
- Fragment: Running through the park. → Fixed: Running through the park, I saw my friend.
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Connect infinitive phrases to a main clause.
- Fragment: To finish the project on time. → Fixed: To finish the project on time, we worked overtime.
Conjunctions and Punctuation
Conjunctions and punctuation are the tools you use to fix run-ons and fragments, so understanding how they work together is essential.
Types of Conjunctions
- Coordinating conjunctions (FANBOYS: for, and, nor, but, or, yet, so) connect words, phrases, or clauses of equal importance.
- Subordinating conjunctions (because, although, if, when, while, since, unless) introduce dependent clauses and link them to independent clauses.
- Correlative conjunctions work in pairs: either...or, neither...nor, both...and, not only...but also.
- Conjunctive adverbs (however, therefore, moreover, consequently) show the relationship between two independent clauses. They're not true conjunctions, so they need a semicolon before them when joining clauses.
Punctuation Rules for Conjunctions
These rules come up constantly, so know them well:
- Comma + coordinating conjunction when joining two independent clauses: I studied hard, and I passed the exam.
- No comma when a coordinating conjunction joins just words or phrases: She likes apples and oranges.
- Comma after the dependent clause when a subordinating conjunction starts the sentence: Although it was raining, we went for a walk.
- No comma when the dependent clause comes second: We went for a walk although it was raining.
- Semicolon before, comma after a conjunctive adverb joining independent clauses: She was late; however, she apologized.
Additional Punctuation Techniques
These go beyond run-ons and fragments, but they help you build more varied sentences:
- Semicolons in complex lists separate items that already contain commas: We visited Paris, France; London, England; and Rome, Italy.
- Colons introduce a list or explanation after an independent clause: He needed three items: a pen, paper, and an envelope.
- Parentheses enclose supplementary information that could be removed: The concert (which lasted for hours) was spectacular.
- The Oxford comma (the comma before "and" in a list of three or more) helps prevent ambiguity: I bought apples, oranges, and bananas.
- You can combine conjunction types to create varied sentence structures: Although it was raining, we went for a walk, but we brought umbrellas. This sentence uses a subordinating conjunction (although) and a coordinating conjunction (but) together.