Punctuation Rules - Quick Reference

Use a comma:

To separate words and phrases that form a series:

• The statue was solid marble, stood ten feet high, and must have weighed two tons.

BUT if the list items are simple, it's preferable to omit the comma before the last element:

• You'll need pens, pencils and notebooks.
• The car had a blue interior, white body and gray pinstripes.

Between elements in dates, addresses and names of places:

• The game on Saturday, October 20, 1988, was the most exciting ever held at Memorial Stadium.
• Send inquiries to 39 Main Street, Box 42, Urbana, Illinois, 61801.
• Columbus, Ohio, is the location of Ohio State University.

BUT omit the commas after the city and state if you use the two-letter state symbol:

• Send inquiries to 39 Main Street, Box 42, Urbana IL 61801.

Between two or more adjectives that modify equally the same noun:

• an intelligent, profitable approach
• the dirty, rusty, dented car

BUT omit the comma if the final adjective is more closely related in meaning to the noun than to the other adjectives:

• ornate electric fixtures (ornate modifies electric fixtures)
• expensive new computer system (expensive modifies new computer system)

Before these conjunctions when they link main clauses (clauses that each have a subject, verb and object):  but   so   yet   or  nor   for  and

• We received your bill, but we can't pay until next week.

BUT omit the comma if two clauses are very short and closely related in meaning:

• Joe turned on the machine but no sound came out.

ALSO omit the comma if the phrase after the conjunction doesn't include a subject word:

• Television advertising is effective but very expensive.
• The mechanic aligned the wheels and adjusted the steering.

To set off these adverbs when they introduce a main clause (a full sentence that could stand alone) or when they are used in mid-sentence to express contrast:  however  indeed  instead  nonetheless  otherwise  still  then  therefore  thus

• Therefore, the manufacturers must approve the contract.
• We will not, however, be able to ship the orders.
• We will be unable to ship the orders, however.

BUT omit the comma for therefore & instead if they fall inside or at the ends of clauses:

• She is therefore willing to negotiate.
• I didn't buy the book; I borrowed it instead.

To set off introductory elements that modify a word in the clause that follows:

• Exhausted, he collapsed on his keyboard.
• Unfortunately, the letter didn't arrive in time.
• If you want to be a clear writer, you must be a clear thinker.
• In 2004, 42 new work stations will be added.

But the comma is optional before short prepositional and infinitive phrases:

• By 2004 the office will be fully networked.
• To write clearly one must think clearly.

To set off a nonrestrictive element -- a word or phrase that gives added information about the words it modifies and could be omitted without changing the essential meaning:

• The library's most valuable book, bought at an auction in 1950, is a 300-year-old Bible.
• Jack, who is an expert typist, will finish this for me.
• This design, which is now an industry standard, will be displayed at the trade show.
• Toole's only novel, A Confederacy of Dunces, won the Pulitzer Prize.
• At noon, our work finished, we took a lunch break.

BUT omit the comma with a restrictive element - a word that limits the meaning of the word it modifies and is essential to the meaning of the sentence:

• The book that I borrowed is due tomorrow.
• Birds flying south signal the end of summer.

Note that clauses beginning with which should almost always be set off with commas.  Clauses beginning with that should not be set off with commas.

To set off expressions of contrast:

• Although the equipment is very expensive, it is necessary.
• Its efficiency, not its cost, should be the main factor.
• This proposal needs more emphasis on performance, less on cost.

BUT omit the comma around simple phrases beginning with but:

• This proposal is long but lacking in evidence.

To set off parenthetical expressions:

• The accountants, for example, never took a lunch break.
• This film is one of Redford's best, according to the critics.

To set off yes and no, tag questions, and words of direct address:

• Yes, we did complete that project.
• The project should be ready tomorrow, shouldn't it?
• Mrs. Jones, could you meet with us on Monday?

Use a hyphen:

If two or more words serve as a single modifier before a noun:

• decision-making process
• Harvard-educated lawyer
• well-known actor
• up-to-date statistics

BUT omit the hyphen if one of the two words is very or an -ly adverb:

• clearly defined policy
• swiftly moving train
• very intelligent woman

For all fractions and compound numbers from 21 to 99:

• three-fourths
• twenty-four

To join the missing parts of two or more parallel compound words:

• eight- and nine-o'clock start times
• Spanish- or English-speaking people
• two-, four- or six-person rooms
• 40-, 60- and 100-megabyte disks

When adding the prefixes self, all and ex (meaning formerly):

• self-control
• all-inclusive
• ex-student

To prevent misreading when adding a prefix or suffix:

• pre-existing
• anti-intellectual
• bell-like

When the root word or the prefix is capitalized:

• un-American
• non-European
• S-shaped

Use a semi-colon:

To link two main clauses (those that could stand alone as full sentences) when the second clause begins with:  however  indeed  instead  nonetheless   otherwise  still  then  therefore  thus

• The orders are due on Friday; therefore, we must ship by Tuesday.
• We can't meet tomorrow; instead, we're planning to meet next week.

To separate items in a series if they are long or contain commas:

• The materials include plywood panels and roofing; cedar siding, trim pieces and accents; and oak beams and rafters.
• The new officers are Bill Smith, president and chief executive; Joe Brown, secretary; Mary Carter, treasurer; and Jane Jackson, recorder.

To closely relate two complete sentences of equal importance:

• He puts in long hours; it's not uncommon to see him here at midnight.
• Low memory usage is only one of the product's advantages; it also offers high speed.

Use a colon:

To introduce statements that explain, repeat or summarize the preceding idea:

• We can't pay because all our money is invested in our home: we own property but have no cash.

To introduce lists that are preceded by the written or implied "the following":

• We reviewed his complaints: the low pay, the long hours and the scheduling problems.
• We need the following materials: cedar siding and trim; plywood paneling; and oak beams and rafters.

BUT omit the colon if a standard verb is used to introduce the list:

• The materials include cedar siding and trim, plywood paneling and oak beams and rafters.
• The new officers are Joe Baker, president; Ann Jones, vice-president; and Tom Lee, secretary.

Use a dash:

In place of a comma or semicolon to add emphasis or show a change in tone:

• He told us -- and we believed him -- that he would never steal from us again.
• Many employees -- especially those at headquarters -- want to move to the new office.
• I soon learned why no one was swimming -- the water was 55 degrees.

In place of a comma or parentheses to set off and emphasize nonrestrictive elements (those that add information but don't change the essential meaning of the noun):

• The materials we need -- plywood panels and cedar siding -- will be here tomorrow.

In place of a colon to add emphasis or informality:

• We liked the home's floor plan - the L-shaped kitchen, the wide hallways, the location of the bedrooms.

Note:  To type a dash, use space-hyphen-hyphen-space.