Run-on Sentences

Run-on sentences contain multiple independent clauses without the punctuation or coordinating conjunction that signals to the reader how, or whether, they're related.

All complete sentences contain at least one independent clause, but may also contain additional elements such as subordinate clauses or coordinating conjunctions. Here are examples of each of these elements:

a clause that can stand alone syntactically as a complete sentence; contains at least a subject and a verb

She ate an apple.

a clause that cannot stand alone as a sentence, but functions as either a noun, adjective or adverb in a sentence

when she ate an apple

a conjunction, such as “and,” “but,” or “or,” that joins two grammatical elements of the same sentence or construction

She ate an apple, but she did not like it.

In order to identify a clause, look for:

The “doer” of the sentence:

He caught the ball.

He caught the ball.

What the action is “done to”:

He caught the ball.

Follow these three steps to find and revise run-ons:

1. Does the sentence contain more than one independent clause? Independent clauses are like mini-sentences, because they can stand alone as grammatically complete expressions. Subordinate clauses cannot stand by themselves; they require an independent clause to form a sentence.
   1. Two independent clauses in run-on sentence:
      I cannot remain silent any longer, the roads have become clogged with bicyclists.
   2. Subordinate clause in correct sentence:
      Although more commuters are using bicycles, there are still too many cars downtown.
   1. Look for sentence boundaries; can you identify where one clause ends and the next begins based on the subjects and verbs? Draw an imaginary line between the independent clauses:
      1. I cannot remain silent any longer, | the roads have become clogged with bicyclists.
      1. Revise the run-on in one of these ways:
         1. Separate the independent clauses with a period or a semicolon.
            1. I cannot remain silent any longer; the roads have become clogged with bicyclists.
            1. I cannot remain silent any longer, for the roads have become clogged with bicyclists.

            Practice Sentences

            First read each sentence and underline all the subjects and circle all the verbs. Then follow the steps in each example to determine whether the sentence is a run-on or not.

            1. Humans have been fascinated by time travel at least since the days of H. G. Wells, Einstein's theories took the notion out of the realm of science fiction.

            Step 1. The sentence contains more than one independent clause.
            Step 2. The independent clauses are as follows: Humans have been fascinated by time travel at least since the days of H. G. Wells, | Einstein's theories took the notion out of the realm of science fiction.
            Step 3. Revise the run-on by changing the punctuation or the conjunction: Humans have been fascinated by time travel at least since the days of H. G. Wells. Einstein's theories took the notion out the realm of science fiction.

            1. One of Wells's most famous novels was The Time Machine it introduced Victorian society to the fascination of time travel.

            Step 1. The sentence contains more than one independent clause.
            Step 2. The independent clauses are as follows: One of Wells's most famous novels was The Time Machine | it introduced Victorian society to the fascination of time travel.
            Step 3. Revise the run-on by changing the punctuation or the conjunction: One of Wells's most famous novels was The Time Machine; it introduced Victorian society to the fascination of time travel.

            1. Einstein declared time to be the fourth dimension, suddenly physicists began to think of traveling in time as they thought of traveling through space.

            Step 1. The sentence contains more than one independent clause.
            Step 2. The independent clauses are as follows: Einstein declared time to be the fourth dimension, | suddenly physicists began to think of traveling in time as they thought of traveling through space.
            Step 3. Revise the run-on by changing the punctuation or the conjunction: Einstein declared time to be the fourth dimension, and suddenly physicists began to think of traveling in time as they thought of traveling through space.

            Last updated 11/19/2020

            Grammar & Style

            • Converting Fragments to Full Sentences
            • Active and Passive Voice
            • Choosing Between Infinitive and Gerund: “To do” or “doing”?
            • Choosing the Correct Word Form
            • Combining Clauses to Avoid Comma Splices, Run-ons, and Fragments
            • Commas, Semicolons, and Colons
            • Count vs. Noncount Nouns
            • Definite and Indefinite Articles
            • Improving Cohesion: The "Known/New Contract"
            • Modal Verbs
            • Parallel Structure
            • Prepositions
            • Pronouns
            • Proper Nouns
            • Reducing Informality in Academic Writing
            • Run-on Sentences
            • Same Form, but Different Functions: Various Meanings of Verb+ing and Verb+ed
            • Subject-Verb Agreement
            • The Three Common Tenses Used in Academic Writing
            • Using Reduced Relative Clauses to Write Concisely
            • Verb Tenses
            • Word Order in Statements with Embedded Questions