Where does a comma go in a sentence

When a date consists of the day of the month followed by the year, the day of the month should be followed by a comma. When the day of the week is provided before the month, the day of the week should be followed by a comma.

When the date appears in the middle of a sentence, commas should appear both before and after the year.

Examples

The store closed its doors for good on Wednesday, October 15, 1958.

Her arrival on Monday, April 11, 1988, was considered a turning point for the company.

When a date is used as an adjective, most authorities require a comma following the year. Yet at least one significant authority (Bryan Garner, in his fourth edition of Garner's Modern English Usage) omits it. Given the uncertainty, it is best to recast the sentence.

Uncertain

The July 10, 2011, meeting was canceled due to a hurricane watch.

Revised

The meeting scheduled for July 10, 2011, was canceled due to a hurricane watch.

No comma is used between the month and the year when they are the only two elements in the date.

Correct

The store closed its doors for good in October 1958.

Incorrect

The store closed its doors for good in October, 1958.

The British style, sometimes used by American writers, reverses the month and day, which eliminates the need for a comma. (See also the essay discussing British and American usage.)

Example

Her arrival on 11 April 1988 was considered a turning point for the company.

The listing comma

Though not necessarily mechanical, the use of commas in lists is well established. In this usage, the comma separates a series of words, phrases, or independent clauses.

Do not place a comma after the last item in the list (see fourth example below) unless the structure of the sentence otherwise requires it (see third example below, in which the comma after audience is required to separate an introductory dependent clause from the main clause).

Examples

For your entree, you may choose vegetarian pasta, beef, chicken, or salmon.

Jane will bring the food, Jose will bring the drinks, John will bring the music, and Jackie will bring the cops.

With dignity, grace, and a tremendous empathy for his audience, he delivered the most moving eulogy.

I am taking art history, Russian literature, microeconomics, and macroeconomics next semester.

The final comma in a list of items is known as an Oxford comma or serial comma. Some writers omit it, but doing so can cause confusion. In the example immediately above, the serial comma makes it clear that the writer is taking two separate economics courses next semester. Omitting the serial comma makes this unclear. Is it one course covering both microeconomics and macroeconomics, or is it two separate courses? Even though not all sentences will be unclear with the omission of the serial comma, its consistent use is a good habit. (See also the essay on style.)

Complex sentences

A complex sentence contains an independent clause and one or more dependent clauses. A dependent clause, unlike an independent clause, cannot stand on its own as a complete sentence. The conjunctions and prepositions most commonly used to introduce a dependent clause include if, because, while, as, although, since, and unless.

Rule: If the dependent clause comes before the independent clause, separate it with a comma.

Examples

If you can’t see without your glasses, you shouldn’t be driving.

Because of the thunderstorm, our flight has been delayed.

Though I don’t doubt his sincerity, I cannot agree with his position on that issue.

When a sentence begins with two dependent clauses that both apply to the subsequent independent clause, insert only a single comma after the second dependent clause.

Example

If you eat a balanced diet and exercise for a few hours each day, you will feel healthier.

Rule: If the independent clause comes before the dependent clause, omit the comma.

Examples

You shouldn’t be driving if you can’t see without your glasses.

Our flight has been delayed because of the thunderstorm.

Exception to the rule: If the dependent clause is not essential to the meaning of the sentence, it should be set off with a comma.

Example

I cannot agree with his position on that issue, though I don’t doubt his sincerity.

Explanation: Not doubting his sincerity is not the reason I cannot agree with his position; it is merely an additional piece of information.

Rule: If the dependent clause occurs in the middle of a sentence, use commas if it is nonessential; do not use commas if it is essential.

Examples

The guests, who were all close friends of the president, refused to speak about the events that evening.

The guests who arrived more than an hour late were greeted coolly by the host.

When comma rules conflict

When you diligently apply the rules described above, you sometimes end up with a sentence nearly bursting with commas. For example:

Example

I originally wanted to be a rock star, but I decided to become an investment banker.

This is a compound sentence (i.e., one with two independent clauses joined by the conjunction but), the rule for which is to insert a comma before the conjunction.

If you want to add a nonessential comment before the second clause, you end up with this:

Example

I originally wanted to be a rock star, but, in the end, I decided to become an investment banker.

This sentence appears to follow the rules described above. There is a comma before the conjunction (but), and the nonessential comment (in the end) is set off with a pair of commas.

There was a time when this sentence would be punctuated exactly this way. Today, such a sentence is considered over-punctuated. There are two schools of thought on how best to lighten the punctuation of such a sentence.

The traditional approach, advocated by William Strunk Jr. in The Elements of Style, removes the comma after the conjunction. Thus:

Example

I originally wanted to be a rock star, but in the end, I decided to become an investment banker.

With this approach, the commas reflect the natural pausing points if the sentence were to be read aloud. Yet some writers object to this. They argue that whatever is inside a pair of commas should be capable of being removed without turning the sentence into nonsense. In this case, applying that test results in this:

Example

I originally wanted to be a rock star I decided to become an investment banker.

That sentence does not make sense. The contemporary school of thought instead removes the comma before the conjunction:

Example

I originally wanted to be a rock star but, in the end, I decided to become an investment banker.

Now when you remove the comma-bracketed material you get:

Example

I originally wanted to be a rock star but I decided to become an investment banker.

The resulting sentence makes sense. But it’s missing the comma that is ordinarily required before the conjunction linking two independent clauses.

What’s the solution? There are at least two possibilities. The nonessential in the end comment doesn’t really need to be bracketed by commas; the meaning is clear enough without them.

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