1. Form the possessive singular of nouns by adding's. Follow this rule whatever the final consonant.

Thus write,

Charles's friend Burns's poems the witch's malice

Exceptions are the possessives of ancient proper names in -es and -is, the possessive Jesus', and such forms as for conscience' sake, for righteousness' sake. But such forms as Moses' laws, Isis' temple are commonly replaced by the laws of Moses the temple of Isis

The pronominal possessives hers, its, theirs, yours, and oneself have no apostrophe.

2. In a series of three or more terms with a single conjunction, use a comma after each term except the last.

Thus write,

red, white, and blue gold, silver, or copper

He opened the letter, read it, and made a note of its contents.

This comma is often referred to as the "serial" comma. In the names of business firms the last comma is usually omitted. Follow the usage of the individual firm.

Brown, Shipley and Co. Merrill Lynch, Pierce, Fenner & Smith Incorporated

3. Enclose parenthetic expressions between commas.

The best way to see a country, unless you are pressed for time, is to travel on foot.

This rule is difficult to apply; it is frequently hard to decide whether a single word, such as however, or a brief phrase, is or is not parenthetic. If the interruption to the flow of the sentence is but slight, the writer may safely omit the commas. But whether the interruption be slight or considerable, he must never omit one comma and leave the other. There is no defense for such punctuation as

Marjorie's husband, Colonel Nelson paid us a visit yesterday.

or

My brother you will be pleased to hear, is now in perfect health.

Dates usually contain parenthetic words or figures. Punctuate as follows:

February to July, 1956 April 6, 1936 Wednesday, November 13, 1929

Note that it is permissible to omit the comma in 6 April 1958

The last form is an excellent way to write a date; the figures are separated by a word and are, for that reason, quickly grasped.

A name or a title in direct address is parenthetic.

If, Sir, you refuse, I cannot predict what will happen. Well, Susan, this is a fine mess you are in.

The abbreviations etc. and jr. are parenthetic and are always to be so regarded.

James Wright, Jr, Letters, packages, etc., should go here

Nonrestrictive relative clauses are parenthetic, as are similar clauses introduced by conjunctions indicating time or place. Commas are therefore needed. A nonrestrictive clause is one that does not serve to identify or define the antecedent noun.

The audience, which had at first been indifferent, became more and more interested.

In 1769, when Napoleon was born, Corsica had but recently been acquired by France.

Nether Stowey, where Coleridge wrote The Rime of the Ancient Mariner, is a few miles from Bridgewater.

In these sentences, the clauses introduced by which, when, and where are nonrestrictive; they do not limit or define, they merely add something. In the first example, the clause introduced by which does not serve to tell which of several possible audiences is meant; the reader presumably knows that already. The clause adds, parenthetically, a statement supplementing that in the main clause. Each of the three sentences is a combination of two statements that might have been made independently.

The audience was at first indifferent. Later it became more and more interested.

Napoleon was born in 1769. At that time Corsica had but recently been acquired by France.

Coleridge wrote The Rime of the Ancient Mariner at Nether Stowey. Nether Stowey is only a few miles from Bridgewater.

Restrictive clauses, by contrast, are not parenthetic and are not set off by commas. Thus,

People who live in glass houses shouldn't throw stones.

Here the clause introduced by who does serve to tell which people are meant; the sentence, unlike those above, cannot be split into two independent statements.

When the main clause of a sentence is preceded by, or followed by, a phrase or a dependent clause, use commas to set off these elements. This rule is similar in principle to the rule governing parenthetic expressions.

Partly by hard fighting, partly by diplomatic skill, they enlarged their dominions to the east and rose to royal rank with the possession of Sicily, exchanged afterwards for Sardinia.

4. Place a comma before a conjunction introducing an independent clause.

The early records of the city have disappeared, and the story of its first years can no longer be reconstructed.

The situation is perilous, but there is still one chance of escape.

Sentences of this type, isolated from their context, may seem to be in need of rewriting. As they make complete sense when the comma is reached, the second clause has the appearance of an afterthought. Further, and is the least specific of connectives. Used between independent clauses, it indicates only that a relation exists between them without defining that relation. In the example above, the relation is that of cause and result. The two sentences might be rewritten:

Because the early records of the city have disappeared, the story of its first years can no longer be reconstructed.

Although the situation is perilous, there is still one chance of escape.

Or the subordinate clauses might be replaced by phrases:

Owing to the disappearance of the early records of the city, the story of its first years can no longer be reconstructed.

In this perilous situation, there is still one chance of escape.

But a writer may err by making his sentences too uniformly compact and periodic, and an occasional loose sentence prevents the style from becoming too formal and gives the reader a certain relief. Consequently, loose sentences of the type first quoted are common in easy, unstudied writing. The danger is that there be too many of them (see Rule 14).

Two-part sentences of which the second member is introduced by as (in the sense of because), for, or, nor, and while (in the sense of and at the same time) likewise require a comma before the conjunction.

If a dependent clause, or an introductory phrase requiring to be set off by a comma, precedes the second independent clause, no comma is needed after the conjunction.

The situation is perilous, but if we are prepared to act promptly, there is still one chance of escape.

When the subject is the same for both clauses and is expressed only once, a comma is required if the connective is but. If the connective is and, the comma should be omitted if the relation between the two statements is close or immediate.

I have heard his arguments, but am still unconvinced.

He has had several years' experience and is thoroughly competent.

5. Do not join independent clauses by a comma.

If two or more clauses, grammatically complete and not joined by a conjunction, are to form a single compound sentence, the proper mark of punctuation is a semicolon.

Stevenson's romances are entertaining; they are full of exciting adventures.

It is nearly half past five; we cannot reach town before dark.

It is, of course, equally correct to write these as two sentences each, replacing the semicolons with periods.

Stevenson's romances are entertaining. They are full of exciting adventures.

It is nearly half past five. We cannot reach town before dark.

If a conjunction is inserted, the proper mark is a comma (Rule 4).

Stevenson's romances are entertaining, for they are full of exciting adventures.

It is nearly half past five, and we cannot reach town before dark.

A comparison of the three forms given above will show clearly the advantage of the first. It is, at least in the examples given, better than the second form, because it suggests the close relationship between the two statements in a way that the second does not attempt, and better than the third, because briefer and therefore more forcible. Indeed, it may be said that this simple method of indicating relationship between statements is one of the most useful devices of composition. The relationship, as above, is commonly one of cause or of consequence.

Note that if the second clause is preceded by an adverb, such as accordingly, besides, then, therefore, or thus, and not by a conjunction, the semicolon is still required.

I had never been in the place before; besides, it was dark as a tomb.

Two exceptions to the semicolon rule are worth noting here. First, when clauses are very short, and are alike in form, a comma is usually permissible:

Man proposes, God disposes.

The gates swung apart, the bridge fell, the portcullis was drawn up.

I hardly knew him, he was so changed. Here today, gone tomorrow.

6. Do not break sentences in two.

In other words, do not use periods for commas.

I met them on a Cunard liner several years ago. Coming home from Liverpool to New York.

He was an interesting talker. A man who had traveled all over the world and lived in half a dozen countries.

In both these examples, the first period should be replaced by a comma, and the following word begun with a small letter.

It is permissible to make an emphatic word or expression serve the purpose of a sentence and to punctuate it accordingly:

Again and again he called out. No reply.

The writer must, however, be certain that the emphasis is warranted, lest his clipped sentence seem merely a blunder in syntax or in punctuation. Generally speaking, the place for broken sentences is in dialogue, when a character happens to speak in a clipped or fragmentary way.

Rules 3, 4, 5, and 6 cover the most important principles that govern punctuation. They should be so thoroughly mastered that their application becomes second nature.

7. A participial phrase at the beginning of a sentence must refer to the grammatical subject.

Walking slowly down the road, he saw a woman accompanied by two children.

The word walking refers to the subject of the sentence, not to the woman. If the writer wishes to make it refer to the woman, he must recast the sentence:

He saw a woman, accompanied by two children, walking slowly down the road.

Participial phrases preceded by a conjunction or by a preposition, nouns in apposition, adjectives, and adjective phrases come under the same rule if they begin the sentence. The examples in the lefthand column, below, are wrong; they should be rewritten as shown in the righthand column.

Sentences violating Rule 7 are often ludicrous:

Being in a dilapidated condition, I was able to buy the house very cheap.