Punctuation is intended to clarify meaning and speed comprehension. Consistency is essential.


Here are a few instances where a period should not be used:

  1. After chemical symbols
  2. After most all-cap abbreviations
  3. After items in a bulleted list that are not complete sentences
  4. After abbreviations of units of measure, except when the unit could be mistaken for a word (e.g., hr, ft; in.)

Use a comma:

  1. Before the conjunction in a compound sentence (a sentence with two or more independent clauses)
  2. After a participial clause, an adverb or an adverbial clause or phrase that comes before the main clause of a sentence. However, if the clause or phrase is short and no confusion results from omitting the comma, it may be omitted.
    Example: In 1999 he joined the faculty of the school of management.
  3. To separate elements in a series, but do not put a comma before the conjunction in a simple series:
    Example: This summer's offerings consist of workshops on technical, commercial and legal librarianship.
  4. Before and after nonrestrictive (nonessential) descriptive or explanatory words, phrases, and clauses
    Example: The endowment, which is the first of its kind in the country, represents a giant step forward for the school.
  5. To separate elements that might otherwise be confused
    Example: Soon after, he sold the house and moved away.
  6. To set off an appositive
    Example: Her husband, John, accompanied her.
  7. In city-state pairs and dates
    Example: He has lived in Cleveland, Tennessee, since 1976.
    Example: I met him on April 7, 1992, to find out why.
  8. To separate digits in numbers greater than 999
    Examples: 1,000; 1,500,735
  9. In a series of related adjectives modifying the same noun, except when those adjectives are commonly used together
    Example: She's a small, thin, gray cat.
    Example: A little old lady lives down the street.

Do not use a comma:

  1. To set off a restrictive (or essential) clause
    Example: The ideas that you have expressed are basically sound.
  2. Between the two parts of a sentence with a compound predicate (two or more verbs with the same subject)
    Example: He went to the University Ball and had a good time.
  3. Before an opening parenthesis
    Example: When he left San Francisco (shortly after the earthquake), he headed for Chicago.
  4. To separate month and year in dates that give only the month and year
    Example: In April 1982, he left for Europe.
  5. To separate season and year.
    Example: He failed a course in fall 2000.
About Colons and Semicolons

The colon is used to mark a break in grammatical construction equivalent to that marked by a semicolon, but the colon emphasizes the content relation between the separated elements. It may be used to indicate a sequence in thought or to introduce an illustration or amplification.


A semicolon denotes a longer pause than that denoted by a comma. Use a semicolon:

  1. Between coordinate clauses that are not joined by a conjunction
    Example: He went to the ball game on Saturday; I came to the office to work.
  2. Between the members of a compound sentence when either one contains elements separated by commas
    Example: And now abideth faith, hope, charity, these three; but the greatest of these is charity.
  3. In a series when one or more of the elements requires a comma
    Example: The wood, pulp, and paper industries; the consumers; and the environmentalists are at odds.
  4. Between clauses joined by conjunctive adverbs, such as therefore, hence, so, however, moreover and accordingly
    Examples: He ran out of money; therefore the job was delayed. He was on time; however, the interviewer refused to see him.

Use a colon:

  1. To introduce a quotation of only one sentence when formality is desired or to introduce a quotation that begins a new paragraph. In general, use a comma instead of a colon before a quotation.
  2. Instead of "to" in ratios, when necessary to save space. No space follows the colon.
    Example: The chemicals are mixed in a ratio of 4:1.
  3. To introduce an example, list or enumeration
  4. Between clauses when one is either an illustration a restatement, or an amplification of the other
    Example: There have been three vice presidents since the administration came to power: This may account for the loss of credibility.

Use an apostrophe:

  1. To form the possessive of most nouns. Note that nouns used as descriptive modifiers do not necessarily require an apostrophe.
    Example: He needed to use the mens room.
  2. With such phrases as a year's work, three weeks' effort, the day's total, a moment's thought
  3. To indicate omission of letters
    Examples: can't, ne'er, rock'n'roll.
  4. In abbreviations of years and decades. Note: Decades may be spelled out.
    Examples: '25, '67, the '60s, the '90s

When forming possessives of singular common nouns which end with s or an s sound, add 's unless the next word begins with an s. When forming possessives of singular proper nouns which end with s or an s sound, use only an apostrophe.
Example: the hostess's invitation, the witness' seat, Achilles' heel, Strauss' suites

Use apostrophes to form the plurals of single letters. Do not use apostrophes to form the plurals of figures, of acronyms or other abbreviations, or of words referred to as words.

Example: Mind your P's and Q's.
She was born in the 1960s.
Example: The RAs were not invited to the party.

Parentheses and Brackets

Use parentheses:

  1. To enclose an irrelevant or incidental comment, information needed to clarify the regular part of the sentence
    Example: It behooves me to say that this staff member (who, by the way, was born in Cleveland) possesses great ability.
  2. Numbers or letters that enumerate divisions of thought. Note that an opening and closing curve should appear around such a number or letter, not just a single curve.
    Example: The reasons for his retirement are (1) advanced age, (2) failing health, and (3) a desire to travel.

If any punctuation is required after the portion of the sentence that precedes the parenthetical matter, put it after the closing curve.
Example: He served the longest term of any president (15 years), becoming a familiar figure on campus.

If an entire sentence is enclosed in parentheses, the final punctuation should be inside the closing curve.
Example: (Additional information appears on page 10.)

If only the last words of the sentence are enclosed in parentheses, the period should be placed after the closing curve.
Example: He uses words improperly (for example, continuous and continual).

Use brackets:

  1. To enclose words inserted in a direct quote by someone other than the author
    Example: "We have to work together to make this [the voluntarism project] successful," he said.
  2. To enclose incidental material that itself is enclosed in a parenthetical passage
    Example: (He told us the reference [found on page 10 of the first edition] was incorrect.)
Quotation Marks

Use quotation marks:

  1. To indicate a direct quotation. A quotation running longer than a few lines may also be indicated by indention and a reduction in type size. If the quotation is treated in this way, quotation marks are omitted. When quotation marks are used to indicate direct quotation, double quotes are used for primary quotations and single quotes for quotations within quotations. In a quotation of more than one paragraph, use opening quotation marks at the beginning of each paragraph and closing marks only at the end of the last paragraph.
    Example: "He said, 'I can't understand why you feel that way,' she explained."
  2. To call attention to a new or unfamiliar word or phrase for which no definition is given. If the word is used frequently, omit the quotes after its first appearance.
    Example: The "new federalism" is a threat to colleges and universities across the country.
    Exception: No quotes are used when a coined word or phrase is introduced by so-called or known as, or when the syntax makes the coinage obvious.
    Example: The dean says his program is distinguished by a feature he calls elective opportunism.
  3. To direct attention to technical or other words used in an unusual context
    Example: He served drinks on the "quarter deck" at the back of the house.
  4. Around nicknames when used with the person's given name (Nicknames generally should not stand alone.)
    Example: C. "Red" Cramer was the University's historian.
  5. Around titles of short compositions, including short poems, articles in periodicals, chapters in books, songs, papers, lectures, and unpublished theses
  6. At the first use of a term when using words as words and when using letters as letters.
    Example: She doesn't know the meaning of the word "work."
    Exception: No quotation marks are used for academic letter grades.

Do not use quotation marks:

  1. Around foreign words. (Use italics.)
    Note: Don't assume an unfamiliar word is foreign. Check the dictionary.
  2. Around the names of ships. (Use italics.)
  3. With slang or original words of your own invention. Omit or translate the slang.
  4. In reference to articles, conferences, books, etc., when the title (full or abbreviated) is preceded by the word "on." Note that "on" is a vague choice indicating that the writer lacks full information.
    Example: He presented a paper on research methods in metallurgy.
    Example: He presented a paper criticizing research methods in metallurgy.
    Example: He presented a paper titled "Research Methods in Metallurgy."
  5. Around words introduced by "so-called" or "known as."
    Example: My so-called mentor forgot I needed her letter of recommendation today.
    Example: This practice, known as waffling, is used by indecisive people everywhere.
  6. When referring to letter grades given for academic course work.
    Examples: She received a grade of A. Acceptance into the program requires a B average.

Some guidelines for the positioning of quotation marks in relation to punctuation marks:

  • Periods and commas always go inside the quotation marks. Other punctuation (dashes, semicolons, colons, question marks, and exclamation points) go inside the quotation marks only when they apply to the quoted material.
    Example: Do you think you can find the answer to the question, "Why is the sky blue?"
    Example: Do you know why he said, "I don't care?"
  • Where quotations within quotations within quotations appear, double and single quotation marks alternate
    Example: "The question is, 'Does his position violate the "gentleman's 'post haste' agreement" so eloquently described by my colleague as "tommyrot?"'"

Following are a few points about quotations in stories such as news articles and student testimonials.

  • In a partial quote, do not put quotation marks around ordinary words that the speaker used.
    Example: Going to school at Western Reserve College was a wonderful experience, she recalled.
  • When attributing a quote that the speaker intended to be humorous, do not insult the reader by announcing that the quote is indeed a joke.
    Wrong: "Teachers are a little like actors. They have to have big egos to get up in front of a class every day," he quipped.
  • Do not strain to find words to replace said. Said is adequate.
    Wrong: "We are making some progress," he summed up.