Commas arguably have become the most widely
misused punctuation mark. Generally, use a comma if one of
the rules below calls for it. You can find these rules, along
with more examples, in Andrea Lunsford's The Everyday
Writer, 5th edition (with exercises), pp. 400-412. For
guidance on the three most common punctuation errors we see in the
Writing Center -- comma splices, fused (run-on sentences), and
sentence fragments -- see pp. 385-396 of the same volume. The
Writing Center has a copy of The Everyday Writer for you
1. Use commas to set off introductory words,
phrases, and clauses.
In fact, healthcare costs keep
Wearing new shoes, Brendan prepared
for the race.
While the storm was raging, we read
(Note that some writers omit the comma after an introductory
element if it is short and does not seem to require a pause after
2. Use commas with conjunctions that join clauses
in compound sentences. A comma usually precedes a
coordinating conjunction (for, and, nor,
but, or, yet, so) that joins
two independent clauses in a compound
The show started late, and the crowd
The title sounds impressive, but
administrative assistant clerk is just another word for
(The comma can sometimes be omitted between short clauses.)
3. Use commas to set
off nonrestrictive elements. Nonrestrictive
elements are clauses, phrases, and words that do not limit, or
restrict, the meaning of the words they modify. Since such
elements are not essential to the meaning of the sentence,
they should be set off with commas.
The two drivers involved in the
accident, who have been convicted of drunken driving,
should lose their licenses.
On the other hand, if a clause, phrase, or word does restrict
the meaning of the words it modifies, it is essential to
the meaning of the sentence, and so we
do not place commas around it.
Drivers who have been convicted
of drunken driving should lose their licenses.
4. Use commas
with items in a series.
He has plundered our seas, ravaged
our coasts, burnt our towns, and destroyed the lives of our
-- The Declaration of Independence
All the cafeteria's vegetables --
broccoli, green beans, peas, and carrots -- were cooked to a gray
(The final comma in a series, often called the serial
comma or Oxford comma, is often omitted in
space-restricted formats such as newspapers.)
(When the items in a series contain commas of their own or other
punctuation, separate them with semicolons rather than
commas: Should I serve kidney beans, which are red; cranberry
beans, which are white and red; or chick peas, which are tan?)
5. Use commas to set off
parenthetical and transitional expressions.
Some studies, incidentally,
have shown that chocolate, of all things, helps prevent tooth
Ozone is a by-product of
dry-cleaning, for example.
6. Use commas
to set off contrasting elements, interjections, direct address, and
Remember, sir, that you are
The governor did not veto the
unemployment bill, did she?
7. Use commas with dates,
addresses, titles, and numbers.
The attacks on the morning of
Tuesday, September 11, 2001, took the United States by
Forward my mail to the Department of
English, The Ohio State University, Columbus, Ohio 43210.
Portland, Oregon, is much larger
than Portland, Maine.
Oliver Sacks, MD, has written about
the way the mind works.
The city's population rose to
158,000 in the 2000 census.
(Do not use commas with dates in inverted order or with dates
consisting of only the month and the year: She dated the
letter 26 August 2008. Thousands of Germans swarmed
over the wall in November 1989. The titles
Jr. and Sr. often appear without commas.
The comma is optional within numerals of four digits but never
occurs is four-digit dates, street addresses, or page numbers.)
8. Use commas to set off
A German proverb warns, "Go to law
for a sheep, and lose your cow."
"All I know about grammar," said
Joan Didion, "is its infinite power."
(Do not use a comma when you introduce a quotation with
that: The writer of Ecclesiastes concludes that "all
is vanity." Do not use a comma after a question mark or
exclamation point: "Out, damned spot!" cries Lady
9. Use commas to prevent
The members of the dance troupe
strutted in, in matching costumes.
Before, I had planned to major in