Rules: (Category I: Punctuation)
1. In a series of three or more terms with a single conjunction, use a comma after each term except the last. E.g.,
red, white, and blue
Exceptions: In the names of business firms, the last comma is usually omitted.
For example,
Little, Brown and Company.
2. Enclose parenthetic expressions between commas.
E.g.,
The best way to see a country, unless you are pressed for time, is to travel on foot.
a) Some abbreviations etc, i.e., and e.g., the abbreviations for academic degree and titles that follow a name are parenthetic and should be punctuated accordingly. Exceptions: Jr.
b) Nonrestrictive relative clauses are parenthetic, as are similar clauses introduced by conjunctions indicating time or place. A nonrestrictive clause is one that does not serve to identify or define the antecedent noun. For example,
The audience, which had at first been indifferent, became more and more interest.
The clauses introduced by which, when, and where are nonrestrictive; they do not limit or define, they merely add something.
Restrictive clauses, by contrast, are not parenthetic and at not set off by commas. For instance,
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 the sentences above, cannot be split into two independent statements.
People sitting in the rear couldn't hear. (restrictive)
Uncle Bert, being slightly deaf, moved forward. (non-restrictive)
c) When the main clause of a sentence is preceded by a phrase or a subordinate clause, use a comma to set off these elements. For example,
Partly by hard fighting, partly by diplomatic skill, they enlarged their dominions to the east and rose to royal ran with the possession of Sicily.
3. Place a comma before a conjunction introducing an independent clause.
E.g.,
The early records of the city have disappeared, and the story of its first years can no longer be reconstructed.
a) Two part sentences of which the second member is introduced by as (in the sense of "because"), for, or, nor, or while (in the sense of "and at the same time") likewise require a comma before the conjunction.
b) 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. For example,
The situation is perilous, but if we are prepared to act promptly, there is still one chance of escape.
c) When the subject is the same for both clauses and is expressed only once, a comma is useful if the connective is but. When the connective is and, the comma should be omitted if the relation between the two statements is close or immediate. For example,
I have heard the arguments, but am still unconvinced.
He has had several years' experience and is thoroughly competent.
4. Do not join independent clauses with a comma.
a) 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. For example,
It is nearly half past five; we cannot reach town before dark.
It is nearly half past five. we cannot reach town before dark.
NOTE that if the second sentence if preceded by an adverb, such as accordingly, besides, then, therefore, or thus, and not by a conjunction, the semicolon is still required. For example,
I had never been in a place before; besides, it was as dark as tomb.
b) An exception of a) is worth noting here. A comma is preferable when the clauses are very shot and alike in form, or when the tone of the sentence is easy and conversational. For example,
Here today, gone tomorrow.
Man proposes, God disposes.
5. Do not break sentences into two.
To be continued ...
Reference
[1] Strunk, Jr., William; E.B. White (1999) [1918]. The Elements of Style (4th ed.). Boston: Allyn & Bacon. p. 60. ISBN 978-0-205-31342-6.OCLC 41548201
a) Some abbreviations etc, i.e., and e.g., the abbreviations for academic degree and titles that follow a name are parenthetic and should be punctuated accordingly. Exceptions: Jr.
b) Nonrestrictive relative clauses are parenthetic, as are similar clauses introduced by conjunctions indicating time or place. A nonrestrictive clause is one that does not serve to identify or define the antecedent noun. For example,
The audience, which had at first been indifferent, became more and more interest.
The clauses introduced by which, when, and where are nonrestrictive; they do not limit or define, they merely add something.
Restrictive clauses, by contrast, are not parenthetic and at not set off by commas. For instance,
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 the sentences above, cannot be split into two independent statements.
People sitting in the rear couldn't hear. (restrictive)
Uncle Bert, being slightly deaf, moved forward. (non-restrictive)
c) When the main clause of a sentence is preceded by a phrase or a subordinate clause, use a comma to set off these elements. For example,
Partly by hard fighting, partly by diplomatic skill, they enlarged their dominions to the east and rose to royal ran with the possession of Sicily.
3. Place a comma before a conjunction introducing an independent clause.
E.g.,
The early records of the city have disappeared, and the story of its first years can no longer be reconstructed.
a) Two part sentences of which the second member is introduced by as (in the sense of "because"), for, or, nor, or while (in the sense of "and at the same time") likewise require a comma before the conjunction.
b) 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. For example,
The situation is perilous, but if we are prepared to act promptly, there is still one chance of escape.
c) When the subject is the same for both clauses and is expressed only once, a comma is useful if the connective is but. When the connective is and, the comma should be omitted if the relation between the two statements is close or immediate. For example,
I have heard the arguments, but am still unconvinced.
He has had several years' experience and is thoroughly competent.
4. Do not join independent clauses with a comma.
a) 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. For example,
It is nearly half past five; we cannot reach town before dark.
It is nearly half past five. we cannot reach town before dark.
NOTE that if the second sentence if preceded by an adverb, such as accordingly, besides, then, therefore, or thus, and not by a conjunction, the semicolon is still required. For example,
I had never been in a place before; besides, it was as dark as tomb.
b) An exception of a) is worth noting here. A comma is preferable when the clauses are very shot and alike in form, or when the tone of the sentence is easy and conversational. For example,
Here today, gone tomorrow.
Man proposes, God disposes.
5. Do not break sentences into two.
To be continued ...
Reference
[1] Strunk, Jr., William; E.B. White (1999) [1918]. The Elements of Style (4th ed.). Boston: Allyn & Bacon. p. 60. ISBN 978-0-205-31342-6.OCLC 41548201
