Improving Your Punctuation

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By brushing up on a few basic rules of punctuation, you will be able to rid your writing of mechanical errors that can seriously affect your grade on an assignment.

Using Commas

Follow this guideline: “When in doubt, leave the comma out.”

  1. Use commas to separate items in a series of three or more words, phrases or clauses.
    Example:
    He bought milk, eggs and cheese.
    She woke up, ate breakfast, and brushed her teeth.
    NOTE: The final comma before the AND is optional, but may clarify your meaning when the series contains internal conjunctions (such as AND or OR).
    Example:
    NO:
    Jane decided to study sociology instead of philosophy, chemistry instead of biology and physics and history instead of geography.
    YES:
    Jane decided to study sociology instead of philosophy, chemistry instead of biology and physics, and history instead of geography. (a final comma before “and history” clarifies the meaning)
  2. Use a comma before a COORDINATING CONJUNCTION (such as and, but, or, nor, for, so, yet) linking two main clauses when the subject is stated.
    Example:
    I don’t want to go out, YET you don’t want to stay home. The professor moved to the front of the room, BUT the students didn’t say a word.
    BUT NOT HERE:
    The professor moved to the front of the room but did not say a word. (becomes a compound verb for one subject)
    NOTE: The comma before a coordinating conjunction will help to clarify whether you have two items in a series OR a conjunction joining two clauses.
    Example:
    NO:
    The first vendor was selling ice cream with chocolate chips and worms were available from the second vendor. (Without the comma, the reader’s first impression is that the ice cream contains chocolate chips and worms.)
    YES:
    The first vendor was selling ice cream with chocolate chips, AND worms were available from the second vendor.
    (The comma here signals the reader that a second subject [worms] is being introduced.)
  3. Use a comma to set off introductory words, phrases and clauses from main clauses.
    Examples:
    Samantha, could you please help me?
    However, he didn’t believe her for one minute.
    Of all the reasons to stay home, that is the most ridiculous.
    Tired from working so hard, she decided to go home.
    Although she was tired, she decided to keep working.
  4. Use a comma (or a pair of commas) to separate from the rest of the sentence any word, phrase, or clause that is not essential to the sentence’s meaning or that means the same as something else in the sentence. (Also see the handout Improving Your Sentence Structure, section A.3.b.
    Example:
    My uncle Fred, who is almost seventy years old, has been sending me presents since I was born.
    Lighting a gas barbecue is easy, I think.
    The Great Dane, a large and gentle dog, is truly one of man’s best friends.
  5. Use a comma between COORDINATE ADJECTIVES (adjectives which each modify the same noun) not joined by AND.
    Example:
    YES:
    Informative, imaginative writing can sell your ideas.
    NOTE: Do not use a comma between the final adjective (imaginative) and the noun (writing). 
    Example:
    NO:
    Informative, imaginative, writing can sell your ideas.
    NOTE: coordinate adjectives are those that still make sense when you insert the word AND between the adjectives or when you scramble the order of the adjectives (i.e., you can write informative and imaginative writing; you can write imaginative, informative writing.)

Misusing Commas

  1. Do not use commas between CUMULATIVE ADJECTIVES (adjectives which build upon each other to modify the noun).
    Example:
    YES:
    The teacher worked on a complex computer program.
    NO:
    The teacher worked on a complex, computer program. ('computer' modifies program, but 'complex' modifies computer program, not just program)
    NOTE: cumulative adjectives are those that no longer make sense when you insert the word AND between the adjectives OR when you scramble the order of the adjectives (i.e., complex and computer program doesn’t make sense; nor does computer, complex program).
  2. Do not use a single comma between a subject and its verb. 
    Example:
    NO:
    The two English courses that I took, were so basic that I never really learned anything.
    YES:
    The two English courses that I took were so basic that I never really learned anything.
    NO:
    The group of nearly twenty members, provides opportunities often not feasible for the independent teacher.
    YES:
    The group of nearly twenty members provides opportunities often not feasible for the independent teacher.
    NO:
    Finding transportation to these programs without the benefit of public transit, is difficult for those who may not have learned to read well enough to obtain a driver’s license.
    YES:
    Finding transportation to these programs without the benefit of public transit is difficult for those who may not have learned to read well enough to obtain a driver’s license.
    NOTE: you may use a PAIR of commas to enclose a nonessential expression between the subject and verb (see section A.4).
    Example:
    YES:
    The two English courses that I took, English 101 and 102, were so basic that I never really learned anything.
    YES:
    The group, which consists of nearly twenty members, provides opportunities often not feasible for the independent teacher.
  3. Do not use a comma between a verb and its object or between a preposition and its object.
    Example:
    NO:
    It is even more interesting when you consider, that several species act the same way.
    YES:
    It is even more interesting when you consider that several species act the same way.
  4. Do not use a single comma AFTER a coordinating conjunction (compare section A.2).
    Example:
    NO: I knew nothing about physics yet, I passed the test easily.
    NO: I knew nothing about physics, yet, I passed the test easily.
    YES:
    I knew nothing about physics, yet I passed the test easily.
    NOTE: you may use a PAIR of commas to enclose a non-essential expression after the conjunction (see section A.4)
    Example:
    YES:
    I knew nothing about physics, yet, thank goodness, I passed the test easily.
  5. Do not use a comma after SUCH AS or LIKE. 
    Example:
    NO:
    We grow many types of fruit trees such as, cherry, apple, orange and banana.
    YES:
    We grow many types of fruit trees such as cherry, apple, orange and banana.
  6. Do not use a comma before a parenthesis. 
    Example:
    NO:
    Mr. Sykes went to see her, (after school) but she was not there.
    NO:
    Mr. Sykes went to see her, (after school), but she was not there.
    YES:
    Mr. Sykes went to see her (after school), but she was not there.

Using Semi-colons

  1. Use a semi-colon between main (independent) clauses that are closely related in meaning and are not joined by a coordinating conjunction.
    Example:
    Mary wishes to major in English literature; her identical twin wishes to major in philosophy.
  2. Use a semi-colon to separate main clauses joined by conjunctive adverbs (such as however, therefore, moreover, nevertheless, then, thus). 
    Example:
    Ernest Hemingway was a master of style; however, opinions about his work vary widely.
    NOTE: The semi-colon remains between the two clauses, even when the conjunctive adverb is moved.
    Example:
    Ernest Hemingway was a master of style; opinions about his work, however, vary widely.
    Ernest Hemingway was a master of style; opinions about his work vary widely, however.
  3. Use semi-colons to separate phrases or clauses in a SERIES if the items are long or contain internal punctuation.
    Example:
    We can help clean up the environment if we avoid littering, polluting, and using throwaway containers; protest against dangers to the environment by writing to those in authority, publicising information, joining groups, and campaigning; plant trees and gardens; and protect endangered species.
    Harry went on a trip with Fred, his uncle; Susan, his sister; Biff, his dog; and his mother.  (Remember to use a semi-colon before the final AND)

Using Colons

  1. Use a colon following an independent clause (i.e., a complete sentence) to introduce a series or a quotation. 
    Example:
    NO:
    The options in the course catalogue are: a major, a major-minor, and a double major.
    YES:
    The course catalogue offers several options: a major, a major-minor, and a double major.
    YES:
    The options in the course catalogue are a major, a major-minor, and a double major.
    NO:
    Hamlet says: “To be or not to be . . .”
    YES:
    Hamlet reveals his doubt and confusion: “To be or not to be . . .”
    YES:
    Hamlet says, “To be or not to be . . .”
  2. Use a colon following an independent clause to introduce a second main clause that explains the first. 
    Example:
    His intention is clear: he plans to get all A’s in his courses.

Using Other Punctuation

  • DASHES are used to emphasize part of a sentence and indicate a break – whether it’s necessary or not – in tone or thought. Type two hyphens with no space before, after, or between, or use your wordprocessor’s “em-dash”
  • PARENTHESES separate incidental information (information you do not need) from the rest of the sentence
  • SQUARE BRACKETS are used to enclose your own comments to “explain, clarify, or correct his [the writer’s] words” within a quotation
  • QUOTATION MARKS are used to enclose direct words of a speaker or exact words from a book or article. Remember that end punctuation, “including commas and periods,” goes “inside the quotation marks”; semi-colons and colons go outside