Punctuation Must Be Parallel
When punctuation is parallel, this means that interrupting a main clause with a dash or a comma requires using the same punctuation at the beginning and end of the clause.
Incorrect: The teenagers, students from Mrs. Smith's art class - went on a field trip to the museum. Correct: The teenagers, students from Mrs. Smith's art class, went on a field trip to the museum. Correct: The teenagers - students from Mrs. Smith's art class - went on a field trip to the museum.
This rule also means that you may not use a semicolon to set off just one item in a list.
Incorrect: I have lived in Des Moines, Iowa, Seattle, Washington; and Boise, Idaho. Correct: I have lived in Des Moines, Iowa; Seattle, Washington and Boise, Idaho.A Dash is a Strong Comma
Essentially, a dash is used for many of the same purposes as a comma. However, since it is more emphatic then a comma, a dash should only be used to add extra emphasis to an important piece of information.
A dash can be used to draw attention to the last item in a list.
For his birthday, Mark received a sweater, a jacket, a savings bond - and a new bike!
A dash can also be used to set off an initial position free modifier that begins with the word "these."
Pizza, chocolate, and ice cream - these are my favorite foods.A Colon Appears at the End of a Completed Main Clause
If you have trouble deciding when to use a colon in your writing, it helps to ask yourself if a period or question mark would be appropriate in the same location. If the sentence is already complete, you may use a colon to add a list, elaboration, or restatement.
List: I have three brothers: David, Kent, and Jacob. Elaboration: I have decided not to move to San Francisco: I have been offered a job in Milwaukee. Restatement: Jenny couldn't decide who was to blame for yesterday's fight: She couldn't decide whether to blame herself or her best friend Annie for the argument.A Semicolon is Used for Equal Emphasis
In a compound sentence that has no coordinating conjunction, a semicolon joins related independent clauses that are of equal importance.
Sarah answered my question abruptly; she seemed preoccupied.
A semicolon can also be used before a conjunctive adverb used to join the two clauses in a compound sentence.
The restaurant was very crowded; however, the waitress took our order immediately.Parentheses Show Related, Nonessential Elements
Parentheses can be used to show elements in a sentence that are related, yet not necessary to understand the meaning of the sentence. Parentheses can be replaced by commas in most cases, although the use of parentheses tends to de-emphasize a particular piece of information.
My family visited several countries (Italy, France, and Spain) on our vacation last year.
If the information inside the parentheses forms a complete sentence within the larger sentence, no punctuation is necessary.
The snow (April saw it when she passed the window) completely covered the trees.Apostrophes Show Possession or Indicate an Omission
An apostrophe is used to indicate possession or ownership. An apostrophe and an -s should be added to singular possessive nouns, plural possessive nouns that do not end in -s, and singular possessive nouns that end in -s. Only an apostrophe should be used when showing possession or ownership for a plural possessive noun that ends in -s.
Singular possessive noun: Susan's bookSingular possessive noun ending in -s: Chris's car Plural possessive nouns: the children's school Plural possessive noun that ends in -s: my parents' house
An apostrophe can also be used to show that a letter has been omitted from a word to form a contraction. For example, "it's" is a contraction for it is. "Its" is a possessive pronoun.
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