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an example of parallel structure

Fixing Writing Errors

Punctuation Points


See Period with abbreviations.

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Apostrophe with plural letters of the alphabet and numerals.

Use an apostrophe with plural letters of the alphabet. The alphabet letter should be italicized. In the following example, however, because the sentence is italicized, the letter is unitalicized.

There are too many t's in this word.

Exception: A plural letter as an academic grade does not require an apostrophe.

With two Ds in math this semester, I wonder if I will be able to graduate in spring.

An apostrophe is not used with numbers as figures or with numbers spelled out.

I need a pair of 8s to win this game.


Apostrophes with possessive compounds and plural words

Only the second word in a possessive compound subject or object gets an apostrophe:

John and Mai's car; Not: John's and Mai's car

Add only an apostrophe to a noun with a plural -s.

the Obamas' home in Hawaii

Apostrophe with possessive nouns ending in an -s sound

Add an apostrophe -s ('s) to a possessive noun ending in an -s or a -z sound.

the bus's passengers  •  Liz's ideas   •  Minneapolis's park system

Exception: for goodness' sake (Chicago Manual of Style)

In general, if you pronounce a possessive -s in speech, add apostrophe -s ('s) to the word when you write it. Careful! In the example below, neither Johns nor Hopkins is plural; Johns Hopkins is an adjective modifying university—not a possessive. No apostrophe is necessary.

Johns Hopkins University

Apostrophe with singular possessive noun

Add an apostrophe -s ('s) to a singular noun to form a possessive noun.

the cat's pajamas  •  day's end

Caution: it's is not a possessive form; the possessive pronoun is its; it's is a contraction of it is or it has.

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Capital letters

Although it is not a feature of punctuation, the proper use of capital letters contributes to readability, the goal of punctuation as well. In addition to proper nouns and the first word of a sentence, capitalize titles of books, films, songs, and other kinds of publications. The first and last words of a title are capitalized. It is not necessary to capitalize short prepositions of fewer than four letters, nor should coordinating conjunctions or articles be capitalized.

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Use a colon to indicate a strong connection between two independent clauses or between an independent clause and a phrase.

  • They lost their house: it was destroyed in a fire.

  • Watch for insects: especially deer ticks and wood ticks.

See also Semicolon.

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Comma after a word or phrase at the beginning of a sentence

A comma is generally not necessary after a short phrase of two or three words at the start of a sentence.

  • The other day I met my former high school principle at the mall. On Wednesday we will meet again.

Use a comma when a lengthy prepositional phrase introduces a sentence.

  • In spite of the budget cuts, the Defense Department spent gross amounts of money on the worthless project.

Use a comma after an adverb of chronology.

  • First, he told me I was working to many hours.

  • Next, he insisted that I needed to change my diet.

Use no comma after then.

  • Then he gave me a prescription to calm my nerves.

Commas between adjectives

Separate adjectives with commas when more than one adjective modifies the same noun in the same way. However, if an adjective forms a compound word with the noun that it modifies, the two words are considered a single unit.

  • Comma required: It was cloudless, sunny day when my car was hit from behind on the freeway.

  • I inadvertently left my blue summer jacket on a bench in the park.

  No comma is required in the previous example because summer jacket is a single unit modified by blue.

Comma or semicolon?

See Semicolon in place of a comma.

Commas with conjunctions

Coordinating conjunctions

Use a comma to separate two independent clauses combined with the coordinating conjunctions and, but, or, for, yet, nor, or so. The comma comes before the conjunction.

  • I love the cinema, but I have not seen many films in recent years.

Generally, do not use a comma before a coordinating conjunction if the subject of the first clause is the same as an omitted subject in the second clause.

  • Rick has never been interested in wildlife and has never gone camping.

Subordinating conjunctions

A comma is not required before a subordinating conjunction, such as because, after, even though, and if when the dependent clause follows the independent clause. However, do use a comma after a dependent clause when it comes before the independent clause in a sentence.

  • Because we know the airline prices are going to increase next month, we are leaving for New York tomorrow.

Correlative conjunctions

Use a comma within a correlative conjunction only when it combines two independent clauses.

  • We were not only the last to arrive, but we were also the last to leave.

  • But: Not only our passports but also our credit cards were stolen.

Adverbial conjunctions

Use a comma to set off an adverbial conjunction from the sentence it modifies.

  • However, I do not accept the notion that everyone needs to see a doctor once a year.

Commas with dates

Comma with American style:

  • January 23, 1919

No comma with international style:

  • 23 January 1919

No comma with month and year:

  • January 1919

Commas with nonessential (nonrestrictive) clauses

Set off nonessential clauses and phrases with commas. In the following two examples, the underlined clause and phrase are nonessential. They are not essential to the meaning of the sentence.

  • Armando, who celebrated a birthday yesterday, lent me his camping equipment for the weekend.

  • Yesterday I bought a new car, a very inexpensive one.

See also Adjective clause in Grammar Snacks.

Comma with three or more elements

Use a comma before the last of three or more items in a sequence.

  • We saw a movie, had dinner at Mai's Cafe, and went canoeing at Sunset Lake.

  • Tim painted each wall a different color: blue, white, yellow, and red.

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Use dashes—or commas—to set off a nonessential or nonrestrictive clause, phrase, or word from the rest of a sentence.

  • The weather on Monday last week—January 10—set three new records.

A dash may be used to indicate a pause.

  • I promise to be on time—if my car starts in this cold weather.

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Ellipsis points or ellipses

Three ellipsis points indicate omitted words.

  • An acquaintance told me that Mr. Murphy is. . .a very serious and reliable employee.

Note: Ellipses are not used to indicate etc.

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Exclamation point

Avoid using an exclamation point unless there is no other way that exceptional emphasis or urgency can be expressed.

  • Fire!

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Hyphens in spelling

In spelling, use a hyphen with numbers twenty-one through ninety-nine. Other compound words may or may not be separated with a hyphen or a space.

  • father-in-law; But: granddaughter, textbook, sales manager.

Check a dictionary if you are unsure whether a compound word is hyphenated, spelled together, or spelled with a space.

Hyphens in word breaks

When the last word does not fit at the end of a line of words, divide the word between syllables that are pronounced clearly.

  • grand-mother, mis-spell, bi-cy-cle, and birth-day.

Do not separate a syllable of only one letter from the next syllable.

  • above, await, atop, emu, over

Avoid separating a final one- or two-letter syllable from the syllable before it.

  • wanted, better, lovely

The -ing suffix may usually be separated from the syllable before it.

  • writ-ing, think-ing, paint-ing

Exceptions with double letters:

  • sip-ping, nap-ping; But: add-ing and spell-ing

Check a dictionary if you are not sure where to divide a word.

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Generally, avoid using parentheses, except when required in technical writing. In academic essays and business writing, parentheses may be used to introduce an initialism or an acronym. After an initialism or an acronym has been introduced in this way, it may be used by itself.

  • The Association of Dairy Products Producers (ADPP) has its annual convention in Milwaukee this year. The ADPP meets in Bismarck next year.

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Period with abbreviations

Use a period after an abbreviation. Exceptions are those abbreviations that are more commonly used than the words they stand for, such as TV or UN. Abbreviations of metric measures do not require periods. Spaces are not necessary between letters followed by periods in an abbreviation. Use a space, however, between initials of a person's name:

  • P. T. Barnum

A sentence ending in an abbreviation with a period does not need an additional period to end the sentence.

  • Mr. Wonka's initials are T. A., not T. E.

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Question mark

Do not use a question mark with requests that use question word order.

  • Would you please turn the volume down on the TV.

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Quotation marks

In American English, put a final period inside a closing quotation mark. A question mark goes inside the final quotation mark if the quotation is a question.

  • “Apparently there is nothing that cannot happen today.” —Mark Twain.

  • “Oh, why are people so crazy?”—Anne Frank

  • But: Who said “The world is a stage”?

The quotations above are indicated with double quotation marks (“”). Use single quotation marks (‘’) to set off a quotation within a quotation in American usage.

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Use a semicolon to bridge two independent clauses when the second clause supports the first. The second clause is not usually capitalized.

  • We had no idea that you were applying for grad school; we thought you were job hunting.

  • I can lend you some money; however, I would need to get it back next month.

See also Colon.

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Semicolon in place of a comma

Use a semicolon in a sentence when an additional comma may slow or confuse a reader.

  • International students in my dorm come from Sapporo, Japan; Lagos, Nigeria; and Doha, Qatar.

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