Effective punctuation starts with the writer making informed choices, not with blindly following a set of rules. To know how to punctuate, you need to know what you want to say and the best way to communicate it. The right punctuation choices help your reader understand your thinking. In most cases, it is best to follow the standard rules and conventions of punctuation, but judgment plays a key role. The nature of the sentence you compose and the ideas you intend to convey determine the punctuation of the sentence.
- Know what you want to say.
- Compose sentences that clearly and concisely show the relationships among your ideas.
- Use punctuation to indicate boundaries between parts of your sentence so that your reader can better understand your ideas.
Terms to Know
An independent clause has a subject and a verb and is logically and grammatically a complete sentence.
My iguana smiled.
A dependent clause has a subject and a verb, but it is not a logically or grammatically complete sentence.
Because I love animals
A compound sentence has two or more independent clauses; compound sentences are used to connect ideas that are closely related and are of equivalent importance.
My iguana smiled, and I smiled back.
A complex sentence has an independent clause plus additional information, often a dependent clause, that helps to develop the precise meaning of the sentence.
My iguana, which I’ve had for nine years, is a great pet.
Single Independent Clause
For a single independent clause with one verb, use end punctuation only.
- Iguanas make nice pets.
- Marco Polo clearly understood the purpose of his journey to the East.
For a single independent clause with multiple verbs:
- Do not use a comma to separate two verbs in a single independent clause.
- Iguanas make nice pets and take up little space.
- Polo spent a great deal of time at the Great Khan’s palace and closely observed its structure.
- Use a comma to separate more than two verbs.
- Iguanas make nice pets, take up little space, and are tidy.
- Polo spent a great deal of time at the Great Khan’s palace, closely observed its structure, and wrote detailed descriptions of the main rooms.
A style note: A string of simple sentences is choppy and monotonous, and it fails to show the relationship between ideas. Consider combining short, related sentences into a more concise construction.
choppy: Iguanas make nice pets. They take up little space.
better: Because iguanas take up little space, they make nice pets.
Introductory Element, Independent (Main) Clause
Use a comma to separate introductory material from the independent (main) clause.
- When my iguana wandered off last weekend, I peered anxiously into every corner of the house.
- Because of his interest in miraculous stories, Polo included the tale of the Church of St. John the Baptist.
Exception: You may omit the comma after a short introductory element as long as the sentence remains clear. Use a comma if any confusion exists.
- During the sixties many independent retail businesses failed.
comma needed for clarity:
- Soon after, my iguana disappeared.
We often combine two independent clauses into a single compound sentence, generally when the ideas are closely related and are of equivalent importance. There are several ways of doing so.
Independent Clause, coordinating conjunction and Independent Clause
(coordinating conjunctions: and, but, for, nor, or, so, yet)
Use a comma to separate two independent clauses joined by a coordinating conjunction.
- Polo commented occasionally on religious buildings, but he focused on descriptions of marketplaces and other structures of economic importance.
Exception: You may omit the comma if the two clauses are short and closely related, as long as the resulting sentence is clear.
- My iguana wandered off and I felt frantic.
Writers sometimes use a semicolon to separate two equal and balanced main clauses joined by a coordinating conjunction when the clauses are long or complex. Doing so makes the sentence easier to read.
- By a conscious effort of the mind, we can stand aloof from actions and consequences; and all things, good and bad, go by us like a torrent. (H.D. Thoreau qtd. in Fowler 496)
A style comment:
Readers appreciate variety. The most popular way of joining two independent clauses in one compound sentence, clause + coordinating conjunction + clause, can get monotonous. Another, more concise way to join two independent clauses is to use a semicolon rather than clause + coordinating conjunction + clause.
Independent Clause; Independent Clause
Use a semicolon to join two independent clauses not joined by a coordinating conjunction (and, but, for, nor, or, so, yet)
- My iguana wandered off; I peered anxiously into every corner of the house.
- Polo reported that the Tibetans were very loyal to their idols; they held elaborate ceremonies on idols’ feast days.
Remember: the two clauses must be logically related and be grammatically complete sentences.
Another way to join two independent clauses in one compound sentence is to use a semicolon plus a conjunctive adverb. A conjunctive adverb can clarify the relationship between the ideas and add important meaning to your sentence.
Independent Clause; conjunctive adverb, Independent Clause.
(common conjunctive adverbs: consequently, finally, furthermore, however, likewise, moreover, nevertheless, therefore, thus)
Use a semicolon to separate two independent clauses joined by a conjunctive adverb. A comma usually follows the conjunctive adverb.
- My iguana wandered off; nevertheless, I didn't worry because I knew she’d return.
- In The Travels, Polo included detailed descriptions of several important religious buildings; however, he focused on descriptions of buildings of political importance such as palaces and forts.
Remember that readers appreciate variety. Just as with a string of simple sentences, a string of compound sentences may seem repetitive. Try varying the sentence structure.
A final note on semicolons:
Semicolons also are used to separate items in a series if the items themselves contain commas.
- She is considering working in New York City, which is expensive; Columbus, which is close to her family; and Taos, which is warm and inviting.
- Main Clause: a, b, and c.
- Main Clause: amplifying information.
Use a colon to separate an independent clause from a list or an amplifying idea.
- On his way to Cathay, Polo met three groups who practiced idolatry: the Tibetans, the Uyghurs, and the Kashmiris.
- I have found one kind of reptile makes a terrific pet: the iguana.
The typical colon error is to use one when no colon is needed. The section preceding the colon must be a grammatically complete sentence.
Correct use of colon
Successful fly-fishing demands specific knowledge: local insect species, their time of hatching, and stream conditions.
Successful fly-fishing demands: knowledge of local insect species, their time of hatching, and stream conditions.
The Serial Comma
To avoid confusion, use commas to separate items in a series, including a comma between the next-to-last and the last item in a series.
- She is considering working in New York, Columbus, or Taos.
If you omit the final comma, you may end up with a confusing sentence:
- I would like to acknowledge my parents, Ayn Rand and God.
Punctuation is a tool to help the writer communicate clearly to readers. This handout discusses some important uses of punctuation; for a fuller discussion of punctuation, refer to a handbook on writing.
For specific advice on punctuation of quotations, see the Hamilton College Style Sheet or the Writing Center handout Quotations.
Fowler, H. Ramsey, Jane E. Aaron, and Janice Okoomian. The Little Brown Handbook, Eighth Edition. New York: Addison, Wesley, Longman, 2001.
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