comma (APA 6th 4.03; see CMS 15th 5.29–5.70 for detailed treatment of specific cases.)
This most common punctuation mark is also the most problematic. Some authorities try to fashion a few general rules to guide us in deciding when to use commas and when not. A good example is APA 6th 4.03, which treats the topic in about one page of loosely spaced type. Other authorities provide dozens, sometimes hundreds of rules in an attempt to be comprehensive. The Chicago Manual of Style, 15th edition, Chap. 5.29–5.70, is a case in point; CMS offers 40 separate rules (and many more specific exceptions) in over 10 pages of small, tightly spaced type.
Although APA's general rules do not cover every case, they are very sensible and are summarized here. If these rules are not specific enough to answer your question, try CMS.
commas and quotation marks (APA 6th 4.08)
Although variations are conceivable, the APA rule here is simple and straightforward: Place commas within quotation marks. Period. Why make things more complicated than this?
Always use a comma
- To separate items in a series. Note that the so-called "optional" comma before the words and and or should always be used in ILA Style (see serial comma):
- Subjects in the experiment spoke French, Vietnamese, and English.
- The idea was developed by Peirce, Dewey, and Whitehead in the 1920s.
- David Lean directed films as diverse as The Bridge on the River Kwai, Lawrence of Arabia,and A Passage to India. (see commas, italic and roman)
- To separate two independent clauses joined by a conjunction:
- The classroom was filled with light, and colorful books filled the shelves.
- Twelve subjects completed the test, but the results were inconclusive.
- To set off nonrestrictive (that is, nonessential) modifiers (see restrictive and nonrestrictive modifiers):
- The first edition, which was published in 1837, was neither a critical nor a commercial success.
- Page proofs, which are prepared after the galleys, incorporate earlier corrections and alterations.
- To set off the year when month, day, and year are given (note commas precede and follow the year). If only the month and year are given, do not use commas:
- Tuesday, January 12, 1982, was a day I will always remember.
- Work on the project was completed between January 1982 and March 1983
- Preceding and following elements in place names, business names, academic degrees, etc.:
- Before moving to Madison, Wisconsin, the author lived in New Delhi, India, with her parents and younger siblings.
- Lima, Peru, is the home of one of the oldest libraries in the Western Hemisphere.
- HarperCollins Publishers, Inc., is located at 10 East 53rd Street, New York, NY.
- Thomas Godfrey Roberts Sr. was born in Ballston Spa, New York, in January 1882. (note exception here).
- Earlene T. Winford, PhD, will be a guest speaker at the conference.
- Exception: This rule has been modified for Jr., Sr., and other generational suffixes.
See entry for Jr., Sr., and numerical suffixes.
- To separate words that might otherwise be misread as closely related:
- After the bear had eaten the zookeeper cleaned its cage. (Do you see a problem here?)
- After the bear had eaten, the zookeeper cleaned its cage. (Do you see the difference?)
- Reading Today reaches every ILA member delivering news about the profession.
- Reading Today reaches every ILA member, delivering news about the profession. (Without the comma, the members are delivering the news. With the comma, RTy is delivering the news.)
- To avoid "squinting modifiers" and similarly ambiguous constructions:
- When space is available on-site registration can be accepted. (As it stands, this sentence is ambiguous. Place a comma after "available" if you are referring to "on-site registration." Place a comma after "on-site" if you are refering to "space on-site.")
Never use a comma
- Between the two parts of a two-part compound predicate:
- The classroom was filled with light and piled to the ceiling with colorful books.
- The class read the passage silently and then composed a brief summary
- Whitman was an ardent admirer of Abraham Lincoln and wrote several poems in memory of the slain president.
- Between a restrictive modifier and the word it modifies (see restrictive and nonrestrictive modifiers):
- The first book that Whitman published was neither a critical nor a commercial success.
- Page proofs that require few alterations may be sent to the indexer immediately.
- After the conjunctions and, but, or, for, so, or yet, unless the comma sets off a parenthetical phrase or clause (i.e., one that interrupts the main idea of the sentence):
- Exceptions are possible, but (not but,) I don't see anything exceptional about this case.
- But (not but,) she managed to win the Nobel Prize for Literature after all, even though the winning novel was her first published work.
- Exceptions are possible but, by definition, quite rare.
commas, italic and roman
- A comma that falls within a title or other italicized matter should be set in italics.
- C.S. Lewis's novel The Lion, the Witch, and the Wardrobe (1950) is an allegory.
- A comma that falls between items in italics should be set in roman.
- C.S. Lewis's allegorical trilogy comprises the novels Out of the Silent Planet, Perelandra, and That Hideous Strength.
Exception: In text published in HTML, punctuation that immediately follows an italicized word or phrase should also be set in italics.