Understanding Sentence Boundaries

Skilled writers use complete sentences to express complete thoughts. A sentence fragment is less than a complete sentence; that is, it is missing one or more elements that make it complete. A run- on is more than a complete sentence; that is, it runs two or more complete sentences together as if they were one.

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​Knowing the differences between complete sentences and sentence fragments is an important part of becoming a strong writer and self-editor.

• A sentence includes at least one independent clause. An independent clause includes a subject and a verb and expresses a complete thought.

Look at these sentences from A Wrinkle in Time:

• She looked around.

• She was completely alone.

• Her heart began to pound.

Each one has a subject (yellow) and a verb (green). Each one expresses a complete thought.

​A sentence fragment may be missing a subject and/or a verb, or it may not express a complete thought.

• Fragment (missing a subject): Beginning to pound.

• Fragment (missing a verb): Her heart in her throat.

• Fragment (not a complete thought): When she realized her situation.

Writers usually use complete sentences to express their meaning. Sometimes, though, a writer chooses to use sentence fragments to produce a specific effect in his or her writing.

This excerpt from A Wrinkle in Time includes two fragments:

• Mrs. Whatsit said to remember that she loves me. That's what I have to think about. Not about being afraid. Or not as smart as IT.

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​Sometimes two or more complete sentences run together as if they are a single sentence. This creates a run-on sentence.

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Like sentence fragments, run-ons are usually avoided, though some writers may use them for effect. For example, using run-ons can show rambling dialogue.

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Run-ons can be confusing because they make it a hard to see where one thought ends and another begins. Alternatively, the connection between the sentences might not be clear.

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​Look at this run-on:

• Madeleine L'Engle wrote many acclaimed books for children and adults, her best-known work, A Wrinkle in Time, won the 1963 Newbery Medal.

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This word group contains two whole sentences (independent clauses) and two whole complete thoughts. With no punctuation between them, the sentences are not clear.

​A run-on can be revised in several ways:

• ​It can be made into two separate sentences:

  Madeleine L'Engle wrote many acclaimed books for children and adults. Her best-known work, A Wrinkle in Time, won the 1963 Newbery Medal.

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• ​A comma and coordinating conjunction (such as and, but, or, so, or yet) can be added, making a compound sentence:

Madeleine L'Engle wrote many acclaimed books for children and adults, and her best-known work, A Wrinkle in Time, won the 1963 Newbery Medal.

• In some cases, the clauses can be joined by a semicolon—if the clauses are closely connected in meaning.

Madeleine L'Engle wrote many acclaimed books for children and adults; her best-known work, A Wrinkle in Time, won the 1963 Newbery Medal.

• Run-ons can also be reworded so that one of the independent clauses becomes a phrase or dependent clause.

Madeleine L'Engle wrote many acclaimed books for children and adults, including her best-known work, A Wrinkle in Time, which won the 1963 Newbery Medal.

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• ​A comma and coordinating conjunction (such as and, but, or, so, or yet) can be added, making a compound sentence:

Madeleine L'Engle wrote many acclaimed books for children and adults, and her best-known work, A Wrinkle in Time, won the 1963 Newbery Medal.

• In some cases, the clauses can be joined by a semicolon—if the clauses are closely connected in meaning.

Madeleine L'Engle wrote many acclaimed books for children and adults; her best-known work, A Wrinkle in Time, won the 1963 Newbery Medal.

• Run-ons can also be reworded so that one of the independent clauses becomes a phrase or dependent clause.

Madeleine L'Engle wrote many acclaimed books for children and adults, including her best-known work, A Wrinkle in Time, which won the 1963 Newbery Medal.

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A compound sentence contains TWO independent clauses that are combined with a conjunction!

• The wide receiver caught the ball, and he danced into the end zone.

• The teacher gave us plenty of time to do the homework, but I forgot it at home.

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​compound sentence

Simple sentences contains ONE independent clause.

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• I finished a book last night.

• ​The train whistled past.

Simple sentence

A compound-complex sentence contains two or more independent clauses and at least one dependent clause.

• When the class was over, Tyler forgot to push in his chair, so Mr. Gilcrest hunted him down.

• ​Without delay, Tyler raced back to the room, and he pushed the chair in nicely like the rest.

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​compound-complex sentence

A complex sentence contains one independent clause and one or more dependent clauses.

• ​When he got to the store, he immediately realized that he didn’t have his wallet.

• Derek Jeter, who plays shortstop for the Yankees, was honored this weekend in the Bronx.

complex sentence