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Sentence-Level Mechanics (Punctuation)

In most instances, place a comma between two sentences that are joined with a coordinating conjunction--and, but, or, for, nor, so, yet:

  • She was not sure if she had the necessary mathematical abilities to be an engineer, so she pursued a graduate degree in history.
  • He was surrounded by fifty people, yet he felt all alone.

You do not need to place a comma between two independent clauses if they are short and similar in meaning, provided that no misunderstanding will take place, as illustrated in the following example:

Learn how to use proper punctuation.

Below is a summary of how to punctuate different sentence patterns and how to analyze the likely effect of different syntactical forms on readers' comprehension.

Commas: Understand conventions for using commas and appreciate the likely effects of particular sentence lengths and patterns on reading comprehension.

Dashes: Create emphasis and define terms by interrupting the flow of a sentence using a dash; know when the dash must be used as opposed to the comma.

Understand conventions for using commas and appreciate the likely effects of particular sentence lengths and patterns on reading comprehension.

Commas are like pawns in chess: They seem relatively insignificant and unobtrusive, yet they are actually very important. If properly placed, the lowly pawn can checkmate the king or, once it has reached the end of the board, become a more powerful piece. Commas play an extremely important role in ensuring that your documents are understandable. In fact, failing to insert a comma in the correct spot can cause considerable misreading (and subsequent embarrassment). Beyond a few special circumstances, there are six basic ways to use commas correctly.

Use a semicolon to join two sentences or to punctuate a series or list of appositives that already includes commas.

The semicolon offers a "higher" form of punctuation than the comma or dash. Unlike commas or dashes, the semicolon can correctly be used to separate sentences. If readers tend to pause for a half-second when they come to a comma, they pause for three-quarters of a second when they reach a semicolon. Writers use semicolons two major ways.

Use the colon when the first sentence anticipates the second sentence or phrase, thereby creating an emphatic tone.

The colon provides a dramatic and somewhat underutilized way to bring a little spark to your writing. Beyond normal business correspondence (Dear Sir or Madam:), you can use the colon before quotations, formal statements and explanations. The colon enables you to highlight a semantic relationship--that is, a movement from a general statement to a specific clarification. The colon also provides a dramatic way to tease the reader's curiosity:

You should limit the number of times that you interrupt the flow of a sentence by placing modifying words between the subject and its verb. When you do introduce such appositives, participial phrases, or adjective phrases or clauses, you must determine whether the modifiers are restrictive or nonrestrictive. Essentially, restrictive modifiers add information that is essential to the meaning of the sentence, whereas nonrestrictive modifiers add information that is not essential. The best way to determine whether a modifier is restrictive or nonrestrictive is to see if taking it out changes the meaning of the sentence.

Restrictive: Lawyers who work for McGullity, Anderson, and Swenson need to take a course in copyediting.

At the end of your sentence, you need to be especially careful about where you place your commas. In particular, you need to question whether the modifying words are restrictive or nonrestrictive. For instance, suppose you received a memo from your writing instructor that said,

  • You should revise the essay, as I suggested.

You could assume that you were directed to revise the essay in any way you deem appropriate. However, if the instructor omitted the comma, then you would be receiving an entirely different message: revise the essay exactly as prescribed by the instructor.

What is an ellipsis?

An ellipsis is a punctuation mark that consists of three dots with a space before, after, and between them. Writers use this mark to represent a word, phrase, sentence (or more) that is omitted from a direct quotation.

How should ellipses be used?

Although our modern style calls for using as few commas as possible, you should generally place a comma after conjunctive adverbs and transitional words because they modify the entire sentence:

  • Nevertheless, we must push forward with our plans.
  • In other words, you're fired. Hey, I'm just kidding.

Because commas cause readers to pause in their reading, you want to use them sparingly.

Use an apostrophe to denote ownership to a singular or plural noun and indefinite pronoun by adding an -'s if the word doesn't end in -s.

Of all forms of punctuation, the apostrophe appears to be in greatest peril of extinction. For proof that the apostrophe should be placed on an endangered species list in some grammarian's office, one needs only to consult the popular press or a sample of student themes. However, because of its ability to denote ownership in a concise way (by avoiding the use of a preposition), the apostrophe plays an important role in the English language. Despite the frequency of its misuse, the apostrophe is a fairly simple form of punctuation to master.

As demonstrated by the following examples, a series is composed of three or more parallel elements, and the series can appear in the beginning, middle, or end of a sentence:

  • Stretching, warming up, and cooling down are important to a good exercise program.
  • All of the necessary qualities of a good assistant -- typing, shorthand, and patience -- she had in abundance.
  • The three qualities of a good introduction are context, purpose, and organization.

What is a hyphen?

A hyphen is a punctuation mark used to bring visual clarity to joined words and word parts in written text. Correct use of hyphens will strengthen the visual appeal of your work and contribute to the readability and clarity of the text as well. To verify hyphen use, refer to a dictionary.

How should hyphens be used?

  • To join some compound words into one word when the word reflects a single concept
    • The well-known doctor gained additional recognition when the results of her top-notch research were published.

What are quotation marks?

One of the primary jobs of quotation marks is to set off exact spoken or written language. When writers use quotation marks correctly, they give credit to the original author and avoid plagiarism. Quotation marks are also used to enclose titles of short works and always appear in pairs.

When and how should quotation marks be used?

What is end punctuation?

End punctuation appears at the end of a complete sentence (independent clause) or follows an interjection. The appropriate placement of a period, question mark, or exclamation point separates one statement from another and signals a pause in the word flow. Correct use of end punctuation contributes to the order and readability of the text.

How should commas be used?

  • Use commas to separate a series of three or more items, actions, words, or phrases.

    • I will need my backpack, computer, paper, and textbook for my next class.
    • Sharon walked across campus, entered the building, and went to class.
  • Use a comma between coordinating adjectives(closely placed adjectives that are of equal importance and describe the same thing).

 What is a dash?

A dash is a punctuation mark used to set off an idea within a sentence and may be used alone or in pairs. Dashes interrupt a thought in a more dramatic way than a phrase enclosed in commas, but less theatrically than parentheses. To form a dash, type two hyphens—without a space before, after, or between them—and your word processor will convert them to a dash.

How should dashes be used?

  • To provide further explanation, clarification, or a summary of the material that comes before the dash

What is an apostrophe?

An apostrophe is a punctuation mark used to show possession, to indicate the plural form of letters of the alphabet, and to form a contraction.

How should apostrophes be used?

  • Use an apostrophe and -s (-’s) to show possession of singular nouns.
    • the author’s main point

What is a semicolon?

A semicolon is a punctuation mark used to separate closely-related independent clauses. Stronger than a comma, a semicolon does not require the use of a coordinating conjunction.

How should semicolons be used?

  • Use a semicolon to link two closely-related independent clauses.
    • Homelessness is a problem that has evaded resolution; despite the heroic efforts of many concerned citizens, there are still thousands left on the streets.

What is a colon?

A colon is a punctuation mark used to separate significant parts of a sentence, particularly when the first part offers a sense of anticipation for the second. This form of punctuation is also used in other conventional applications as noted below.

How should colons be used?

Understand conventions for using commas and appreciate the likely effects of particular sentence lengths and patterns on reading comprehension.

Commas are like pawns in chess: They seem relatively insignificant and unobtrusive, yet they are actually very important. If properly placed, the lowly pawn can checkmate the king or, once it has reached the end of the board, become a more powerful piece.

Parentheses (also called brackets in British English) are a punctuation mark used to contain text that is not part of the main sentence, but that is too important to either leave out entirely or to put in a footnote or an endnote. Since there are many reasons to use parentheses, be sure that the function of parentheses is always made clear to your readers.