Can somebody please help me by explaining or providing a reference which explains the punctuation in the following sentences.

We prefer no article when we are thinking about unlimited numbers or quantities or not thinking about numbers/quantities at all.

“I read romance and fantasy and write science fiction.”

Where should I put commas in the above sentences? They have the following structure: X [A and/or B] and/or Y. Second and/or links words (X and Y) that are unrelated to A and B. Will the punctuation rule here be the same for both and and or conjunctions?

PS I can't think of a proper title for this question – maybe somebody can edit it.

  • The modern trend is to reduce comma usage (except where a comma is being used to replace what might once have been a full stop), so at least some writers wouldn't include any commas in your cited example. Most would put one after fantasy (to clearly delineate the boundary between what you read from what you write), but it's really just a matter of personal preference / chosen style guide / opinion. Aug 6, 2015 at 17:24
  • Why write "numbers or quantities" and then in the same sentence "numbers/quantities"?
    – TimR
    Aug 6, 2015 at 17:26
  • @FumbleFingers -- it's not really a stylistic choice, to put a comma after fantasy -- see my answer below. Of course, everything can be a stylistic choice if it works.
    – ewormuth
    Aug 6, 2015 at 17:36
  • @Tim This is a sentene I encountered while reading Practical English Usage (Third Edition, page 58) by Michael Swan. I don't know why he decided to write it this way. Aug 6, 2015 at 17:50
  • @ewormuth: I've duly read your answer below, but I'm none the wiser as to why you dispute my personal preference / chosen style guide / opinion categorisation. Aug 6, 2015 at 17:56

2 Answers 2


In both sentences, you have two-part parallel constructions. As a general rule, don't put a comma in the middle of a two-part structure:

From Professor John Fleming at DeAnza College:

B. Two of any parallel structures other than independent clauses are separated by a coordinating conjunction only:

Fred and George want to see Mary. (nouns) Mary got in her car and drove away. (verbs) I don’t know where she is or when she will return. (subordinate clauses)

A comma is rarely used between just two parallel structures. Only a coordinating conjunction is used between two parallel structures (unless they are independent clauses as in A. above).

Exception: a comma is sometimes used between two adjectives which precede a noun. For example:

It is a dark, ugly room.

So in your first example above, you would not put a comma between numbers or quantities or between thinking about unlimited numbers or quantities and not thinking about numbers/quantities at all.

In the second sentence, you would not put a comma between romance and fantasy or between read romance and fantasy and write science fiction.

Others may disagree, but I wouldn't put a comma between article and when, because what follows article is essential to the sentence's meaning.

Purdue OWL explains this rule:

Rule: Use commas before and after nonessential words, phrases, and clauses, that is, elements embedded in the sentence that interrupt it without changing the essential meaning. If you leave out the element or put it somewhere else in the sentence, does the essential meaning of the sentence change? If so, the element is essential; if not, it is nonessential.

Where commas are concerned, the fewer the better. An old prof of mine would say "Don't use a comma unless you feel absolutely compelled to do so." Maybe not a great rule, but it's helped me.

  • Thank you for your answer, and I found DeAnza College reference very helpful. Aug 19, 2015 at 0:55

My MO is to avoid questionable syntax in the first place. Repairing it or clarifying it with punctuation is a kludge. If you find yourself wondering how to punctuate, revise.

Whenever I completely change direction, as the first sentence does, I opt for an em-dash instead of a comma. But I'd repeat the "when":

We prefer no article when we are thinking about unlimited numbers or quantities — or when not thinking about numbers and quantities at all.

With "write" versus "read" in the second sentence, the opposition seems less stark than that in the first sentence (thinking...not thinking ...at all) so there it gets a little fuzzy; I'd probably skip the comma but repeat the pronoun "I"

... and I write science fiction.

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