Comma Rule

[vcolts]

E.g. Viruses are consisted of a nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope.

Do I need a comma before "in some cases"? If yes, why?


Thanks in advance.

[Kondorosi]

E.g. Viruses are consisted of a nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope.

Do I need a comma before "in some cases"? If yes, why?


Thanks in advance.

I would apply the comma thus:

Viruses are consisted consist of a nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope.

The arrangement of information is not so complex that you need many commas.

If you put a comma before 'and', the reader will break his neck. Too many stops. However, I would set off 'in some cases' by a set of commas.

[bhaisahab]

I would apply the comma thus:

Viruses are consisted consist of a nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope.

The arrangement of information is not so complex that you need many commas.

If you put a comma before 'and', the reader will break his neck. Too many stops. However, I would set off 'in some cases' by a set of commas.

I agree.

[vcolts]

Erm, I didn't ask if i need a comma before "and" but after "and". Also, I am more focused on learning as to why you would need it. So I would like to know the precise comma rule for why I need a comma before and.

[Gillnetter]

E.g. Viruses are consisted of a nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope.

Do I need a comma before "in some cases"? If yes, why?


Thanks in advance.

In some cases is an independent clause. The text can function as a sentence without this clause. A comma is inserted before " in some cases" to set it apart from the rest of the sentence. Read the sentence with "in some cases" taken out.

[Raymott]

In some cases is an independent clause. The text can function as a sentence without this clause. A comma is inserted before " in some cases" to set it apart from the rest of the sentence. Read the sentence with "in some cases" taken out.

"In some cases" is a prepositional phrase.
In what sense is it a clause? And independent?

As you imply, a parenthetical or interpolated phrase such as this requires surrounding commas, and the sentence should make sense if the phrase and the commas are removed.
But that makes the sentence independent of the phrase, not vice versa.

[vcolts]

Getting mixed answers on this one.

I did some search for example sentences, and they vary a lot it seems. A lot of them were missing the commas.

A link would be helpful in understanding why.

[Raymott]

Getting mixed answers on this one.

I did some search for example sentences, and they vary a lot it seems. A lot of them were missing the commas.

A link would be helpful in understanding why.

The commas are often optional, especially in a short sentence.
However, with a parenthetical phrase, if you use one comma you must use two - like brackets.

It's surrounded in some cases by a membranous envelope.
It's surrounded, in some cases, by a membranous envelope.

The above are both correct, but in your original longer sentence, the commas are preferable.

The use of commas for a parenthetical phrase is similar to the use of parentheses or dashes, as below. We wouldn't write the sentence as below, but it reinforces why the two commas (or none) are necessary.
It's surrounded (in some cases) by a membranous envelope.
It's surrounded - in some cases - by a membranous envelope.