The comma is by far the most difficult of all the punctuation marks to use correctly. Usage varies greatly from time to time and among equally good writers and printers at the same time. Certain general rules may be stated and should be learned. Many cases, however, will arise in which the rules will be differently interpreted and differently applied by different people.
The comma is the least degree of separation possible of indication in print. Its business is to define the particles and minor clauses of a sentence. A progressive tendency may be seen in the printing of English for centuries toward the elimination of commas, and the substitution of the comma for the semicolon and of the semicolon for the colon. Compare a page of the King James version of the Bible, especially in one of its earlier printings, with a page of serious discourse of to-day and the effects of the tendency will be easily seen. It is part of the general tendency toward greater simplicity of expression which has developed the clear and simple English of the best contemporary writers out of the involved and ornate style of the period of Queen Elizabeth. An ornate and involved style needs a good deal of punctuation to make it intelligible, while a simple and direct style needs but very little help.
This progressive change in the need for punctuation and in the attitude of writers toward it accounts for the difference in usage and for the difficulty in fixing rules to cover all cases. The present attitude toward punctuation, especially the use of the comma, is one of aversion. The writer is always held to justification of the presence of a comma rather than of its absence. Nevertheless it is quite possible to go too far in the omission of commas in ordinary writing. It is quite possible to construct sentences in such a way as to avoid their use. The result is a harsh and awkward style, unwarranted by any necessity. Ordinary writing needs some use of commas to indicate the sense and to prevent ambiguity.
Always remember that the real business of the comma is just that of helping the meaning of the words and of preventing ambiguity by showing clearly the separation and connection of words and phrases. If there is possibility of misunderstanding without a comma, put one in. If the words tell their story beyond possibility of misunderstanding without a comma, there is no reason for its use. This rule will serve as a fairly dependable guide in the absence of any well recognized rule for a particular case, or where doubt exists as to the application of a rule.
Reversed, and usually in pairs, commas mark the beginning of a quotation.
In numerical statements the comma separates Arabic figures by triplets in classes of hundreds: $5,276,492.72.
The comma is placed between the words which it is intended to separate. When used in connection with quotation marks, it is always placed inside them.
“Honesty is the best policy,” as the proverb says.
Rules for the Use of the Comma
1. After each adjective or adverb in a series of two or more when not connected by conjunctions.
He was a tall, thin, dark man.
The rule holds when the last member of the series is preceded by a conjunction.
He was tall, thin, and dark.
The comma may be omitted when the words are combined into a single idea.
A still hot day.
An old black coat.
2. After each pair in a series of pairs of words or phrases not connected by conjunctions.
Sink or swim, live or die, survive or perish,
I give my hand and my heart to this vote.
Formerly the master printer, his journeymen,
even his apprentices, all lived in the same house.
3. To separate contrasted words.
We rule by love, not by force.
4. Between two independent clauses connected by a conjunction.
The press was out of order, but we managed to start it.
5. Before a conjunction when the word which preceded it is qualified by an expression which does not qualify the word which follows the conjunction.
He quickly looked up, and spoke.
6. Between relative clauses which explain the antecedent, or which introduce a new thought.
The type, which was badly worn, was not fit for the job.
If the relative clause limits the meaning of the antecedent, but does not explain it and does not add a new thought, the comma is not used.
He did only that which he was told to do.
7. To separate parenthetical or intermediate expressions from the context.
The school, you may be glad to know, is very successful.
The books, which I have read, are returned with gratitude.
He was pleased, I suppose, with his work.
If the connection of such expressions is so close as to form one connected idea the comma is not used.
The press nearest the south window is out of order.
If the connection of such expressions is remote, parentheses are used.
The Committee (appointed under vote of April 10, 1909) organized and proceeded with business.
8. To separate the co-ordinate clauses of compound sentences if such clauses are simple in construction and closely related.
He was kind, not indulgent, to his men; firm, but just, in discipline; courteous, but not familiar, to all.
9. To separate quotations, or similar brief expressions from the preceding part of the sentence.
Cæsar reported to the Senate, “I came, I saw, I conquered.”
The question is, What shall we do next?
10. To indicate the omission of the verb in compound sentences having a common verb in several clauses.
One man glories in his strength, another in his wealth, another in his learning.
11. To separate phrases containing the case absolute from the rest of the sentence.
The form having been locked up, a proof was taken.
12. Between words or phrases in apposition to each other.
I refer to DeVinne, the great authority on Printing.
The comma is omitted when such an apposition is used as a single phrase or a compound name.
The poet Longfellow was born in Portland.
The word patriotic is now in extensive use.
13. After phrases and clauses which are placed at the beginning of a sentence by inversion.
Worn out by hard wear, the type at last became unfit for use.
Ever since, he has been fond of celery.
The comma is omitted if the phrase thus used is very short.
Of success there could be no doubt.
14. Introductory phrases beginning with if, when, wherever,whenever, and the like should generally be separated from the rest of the sentence by a comma, even when the statement may appear to be direct.
When a plain query has not been answered, it is best to follow copy.
If the copy is hard to read, the compositor will set but few pages.
15. To separate introductory words and phrases and independent adverbs from the rest of the sentence.
Now, what are you going to do there?
I think, also, Franklin owed much of his success to his strong common sense.
This idea, however, had already been grasped by others.
Of course the comma is not used when these adverbs are used in the ordinary way.
They also serve who only stand and wait.
This must be done, however contrary to our inclinations.
16. To separate words or phrases of direct address from the context.
I submit, gentlemen, to your judgment.
From today, my son, your future is in your own hands.
17. Between the name of a person and his title or degree.
Woodrow Wilson, President of the United States.
Charles W. Eliot, LL.D.
18. Before the word of connecting a proper name with residence or position.
Senator Lodge, of Massachusetts.
Elihu B. Root, Senator from New York.
19. After the salutatory phrase at the beginning of a letter, when informal.
When the salutation is formal a colon should be used.
My dear Mr. Smith:
20. To separate the closing salutation of a formal letter from the rest of the sentence of which it forms a part.
Soliciting your continued patronage, I am,
Very sincerely yours,
John W. Smith.
21. To separate two numbers.
January 31, 1915.
By the end of 1914, 7062 had been built.
22. To indicate an ellipsis.
Subscription for the course, one dollar.
Exceptions to this rule are made in very brief sentences, especially in advertisements: Tickets 25 cents. Price one dollar.
The foregoing rules for the use of the comma have been compiled from those given by a considerable number of authorities. Further examination of authorities would probably have added to the number and to the complexity of these rules. No two sets of rules which have come under the writer’s observation are alike. Positive disagreements in modern treatises on the subject are few. The whole matter, however, turns so much on the use made of certain general principles and the field is so vast that different writers vary greatly in their statements and even in their ideas of what ought to be stated. It is very difficult to strike the right mean between a set of rules too fragmentary and too incomplete for any real guidance and a set of rules too long to be remembered and used.
After all possible has been done to indicate the best usage it remains true that the writer or the printer must, in the last resort, depend very largely on himself for the proper application of certain principles. The compositor may find himself helped, or restricted, by the established style of the office, or he may at times be held to strict following of copy. When left to himself he must be guided by the following general principles:
I. The comma is used to separate for the eye what is separate in thought.
The comma is not intended to break the matter up into lengths suited to the breath of one reading aloud.
The comma is not an æsthetic device to improve the appearance of the line.
II. The sole purpose of the comma is the unfolding of the sense of the words.
III. The comma cannot be correctly used without a thorough understanding of the sense of the words.
IV. In case of doubt, omit the comma.
And that’s it from Frederick W. Hamilton on the subject of the comma. Next, the semicolon.