End Punctuation

Use end punctuation to signal the end of a sentence. The three end marks are a period, a question mark, and an exclamation point:

The engine sounds noisy.

Does the engine sound strange to you?

That sounds like a broken fan belt!

Periods are the most commonly used end punctuation; occasionally, they can mark off a sentence fragment when you want to achieve a particular rhe­torical effect:

sentence: There is only one man who had the motive, the opportunity, the technical knowledge, and the utter lack of humanity to kill poor Mrs. Sappington.

fragments: Only one man. Otis Armstrong.

Question Marks are used at the ends of sentences that are direct questions. (Indirect questions are embedded in whether or if clauses and are ended with periods or, occasionally, exclamation points.)

direct question: Do you want a chocolate chip cookie? Do you know what he wants?

indirect question: I don't know whether he wants a chocolate chip cookie or not.

fragment: Chocolate chip cookie? What chocolate chip cookie?

Exclamation Points are used—occasionally—to signal the end of a sentence that expresses surprise or other strong emotions:

sentence: I love carrot cake!

fragment: Carrot cake! Yummie!

Commas

With Coordinating Conjunctions

Use a comma to join coordinate clauses when a coordinating conjunction precedes the second clause. The coordinating conjunctions are and, but, so, yet, for, or, and nor:

The low wage didn't depress her, but the high cost of living did. Having her own apartment and her own car delighted her, and, in addi­tion, her job was a challenge.

In Series

Use commas to separate the items in a series of words, phrases, or clauses of roughly equal importance:

They landed on the space station Ariadne despite an attack by an alien space ship, an epidemic of a fatal cosmic disease, an accidental time rever­sal, and an engine failure of monumental proportions.

Use commas to separate a series of coordinate adjectives but not a series of uncoordinate adjectives. The adjectives are coordinate if and can be inserted between the adjectives, and if the order of the modifiers can be reversed.

Eve felt a substantial, hard, definite lump in her old jacket pocket.

could logically be:

Eve felt a substantial and hard and definite lump in her pocket.

Eve found a red sandstone rock in her old jacket pocket.

could not be:

Eve found a red and sandstone rock....

With Introductory Modifiers

Use a comma between an introductory modifier and the rest of the sentence:

Finally, the car started.

Although Joel knew her, Beth didn't know him.

Under the family room, there dwelt a family of mice.

Weaving in and out of the crowd, Martha finally caught up with him.

Do not confuse a gerund phrase that functions as the subject of the sentence with a participial phrase:

gerund subject: Weaving the purple shawl was a pleasure for Martha.

participial phrase: Having finished the purple shawl, she rested.

With Nonrestrictive Modifiers

Use commas to set off nonrestrictive modifiers, but do not use them with restrictive modifiers. A restrictive modifier is one that defines or limits the word it modifies, while a nonrestrictive modifier is one that adds information that is interesting but not necessary to understand the word in question. Nonrestric­tive modifiers may be words, phrases, or clauses:

restrictive: The woman whom he had loved for ten years came back.

nonrestrictive: The blue violets, which are Aunt Ella's favorites, bloomed.

restrictive: The girl with the tousled curls came too.

nonrestrictive: The girl came too, with hair tousled and hands dirty.

restrictive: The child dressed in a bear costume frightened the dog.

nonrestrictive: Colin, dressed like a space man, behaved himself.

restrictive: The post lady is always late when she brings my check.

nonrestrictive: Miles loves the post lady, whenever she comes.

restrictive: Our dog Don won a blue ribbon, but our Fifi did not.

nonrestrictive: Don, our Labrador retriever, is a very loving dog.

With Concluding Modifiers

Always separate concluding modifiers such as absolute and participial phrases from the main clause with commas:

Darnell is an engineer whose mechanical aptitude decreases with each step he takes closer to home, his most famous repair resulting in routing hot water into the garden hose.

With Transitional Expressions

Use commas to separate conjunctive adverbs and other transitions from the rest of the sentence, regardless of where in the sentence they appear:

Companies, however, are very specific.

Still, women account for only four to five percent of management.

In Direct Address

Use commas to set off the names of people being addressed:

Dr. Dearden, you know I tried hard!

We will go to Hawaii, Mr. Selleck, if you agree.

With Interjections

Use commas to set off interjections:

The Double Brass Band, as the name implies, is big and loud.

To Separate Quoted Matter

Commas that follow quotations should be placed inside the quotation marks. Commas separate nonquoted material from quoted matter:

"Dr. Nesbitt," they cried in unison, "let us hand our papers in next week!";

In Titles, Addresses, and Dates

When a person's name is followed by a degree or other title, it should be set off by commas:

Martin Luther King, Jr. Elizabeth Barnes, Ph.D.

When a name with a title is part of a sentence, use a comma after the title as well:

The seminar speaker will be Jesse Billings, M.D., from Ohio.

Use a comma to set off the day of the month and the year:

I will arrive in Spain on May 15, 1985, at 10:45 a.m.

But omit the comma if only the month and year are used:

I will arrive in Spain May 1985.

Use commas to separate the elements in an address excepting the zip code:

My father has lived in Dedham, Massachusetts, all his life. His address is 123 Windsor Rd., Dedham, MA 02162