Dave's ESL Cafe's Student Discussion Forums

[Chan-Seung Lee]

[Anuradha Chepur]

You need a comma, since they are two sentences joined by a conjunction, 'both.' The sentence is alright with 'about', but you still need a comma before it, as it is a long sentence. Both is more suitable than about, though.

[Mary W. Ng]

[Anuradha Chepur]

The general understanding is that we put a comma depending on whether the clause is defining or non-defining. Labelling a clause as defining or non defining depending on whether we have chosen to put a comma or not is new to me.
Interesting, anyway.

[lotus]

Hi,

Restrictive (defining) and non-restrictive (non-defining) clauses are determined by the existence of a comma.
http://grammar.ccc.commnet.edu/grammar/clauses.htm#restrictive

When a comma is there, it's non-restrictive (not essential to the meaning of the sentence). When a comma's not there, it's restrictive (essential to the meaning of the sentence).
http://www.english.uiuc.edu/cws/wworkshop/writer_resources/grammar_handbook/restrictive_non_clauses.htm#nonrestrictive

The existence of the punctuation determines the nature of the clause. The writer punctuates depending on his/her intent. Most of the time, the wording of the clause can indicate whether it's restrictive or non-restrictive. Still, proper punctuation must be used to avoid confusion.
http://www.ucalgary.ca/UofC/eduweb/grammar/course/punctuation/3_4c.htm

Sometimes, the clause can be ambiguous and we have to use the proper punctuation to indicate our meaning.
http://www.bartleby.com/68/32/5132.html

Sometimes, we use "that" or "which" to help indicate whether the clause is restrictive or non-restrictive (although I don't recommend it, because the relative pronoun "that" has been over-used and the distinction has lost its meaning).
http://www.bartleby.com/68/91/5991.html

Since we can't read the writer's mind, the writer must use the proper punctuation to indicate whether a clause is essential or not essential to the meaning of the sentence. Barring obvious context, the reader can only interpret the writer's intent through the existence (or non-existence) of the punctuation.

#3 does not need punctuation. "About..." is a prepositional phrase modifying "opinions" and does not need a comma to set it off.


--lotus
_________________
War does not make one great --Yoda

[Anuradha Chepur]

The links provided only tell us to set off a non-restrictive clause with a comma.
In any case, the clause introduced by both in the OP is non-essential to the main clause. It can be removed from the sentence and the main clause would make sense on its own. So we need a comma there. The clause introduced by both, is referred to by some as a 'trailing dependent clause' that enhances the meaning of the sentence. They recommend setting it off with a comma so it doesn't get lost in the sentence, specially if it's a longish sentence. The sentence is too long to say it without a pause.