The comma (,) denotes a short pause. Commas are used for the following.
1. To separate items in a list or series;
- January, February, and March are the first three months of the year.
2. Words, phrases, or clauses in a series (and co-ordinate adjectives modifying the same noun) are separated by commas.
- I looked inside the hall and it was bright, clean, and quiet.
(Note that commas are omitted when and is used throughout the series)
- A man has a duty to himself, to his family, and to the State.
- When the day dawned, when the sun rose, when the mist cleared, then we realized that our great opportunity had come.
3. The comma is used to set off the name of the person addressed.
- Why have you not travelled, John?
- John, come here!
4. As a rule, appositives are set off by commas.
- Cheerfulness is health; the opposite, melancholy, is disease.
5. Titles and degrees after a name are set off by commas.
- S.E. Thomas, B. Com ., Ph.D ., A.I.B, F.C.I.S ., is one of the authors of English Grammar, Composition and Correspondence.
6. Most parenthetical expressions are set off by commas; for example:
however, on the other hand, therefore, for instance, by the way.
- The man, however, was not to blame.
- The girl, who spoke to you, is our secretary.
Commas are often used instead of dashes or brackets to mark of parenthesis, but if the parenthesis is lengthy it is more helpful to the reader if brackets or dashes are used instead of commas.
7. Use a comma after yes or no at the beginning of a sentence.
- Yes, you were there.
8. Commas are used to mark the omissions of some word or groups of words that are understood.
- General Haig was the commander of the British:General Petain of the French; and General Pershing, of the Americans.
- We respect deeds; they, words.
9. The comma is used after the salutation of a friendly letter and the complimentary close of any letter.
- Dear Mr. Peters,
- Yours sincerely,
10. Occasionally, when no other rule justifies the use of a punctuation mark, a comma is necessary to prevent misreading.
- Ever since, Zion House has been occupied.
- The night before, we bought a tent to take with us.
- To the wise, youth is a time for training.
11. Commas are used in direct speech where a break is made in the speech to indicate who is speaking.
- “Come,” said the boy, “we shall find it.”
- “She is arriving tomorrow, “John replied.
12. A subordinate clause (or a long phrase) preceding the main clause is usually followed by a comma.
- Although I am not a member of the club, I know much of its history. (Subordinate clause preceding the man clause.)
- After a long apprenticeship in good words and study of the sacred books, he was ordained a priest. (A long phrase preceding the main clause.)
13. Introductory phrases containing a gerund, a participle, or an infinitive, even though short, must be followed by a comma to prevent misreading.
- Before leaving, the soldiers demolished their camp.
- Because of his effort to escape, his punishment was increased.