This city has experienced a decrease of 1% per year in the visibility, a meteorological parameter partly affected by atmospheric pollution.

I would like to include the parenthetical clause to introduce the concept of 'visibility', as it is just a minor point, I don't want to start another sentence for it. However, by doing so, the trend description reads a little bit odd to me. Is it grammatical?

  • Your sentence is repetitive. It starts by telling the reader that atmospheric pollution has reduced visibility in the city and then it says that such pollution affects visibility. Obviously, if the pollution has reduced visibility, it affects visibility - even if it's not the only factor. You could greatly simplify the sentence without losing the content. Commented Oct 16, 2019 at 18:17
  • Thank you for your reply. Actually, 'due to atmospheric pollution' was not in the original sentence. I thought it would make the context clearer for people who read my post. Things go contrary to my wishes, haha. I deleted it. How about now?
    – Elizabeth
    Commented Oct 16, 2019 at 18:49
  • 1
    There is nothing wrong with your sentence. (Idiomatically, however, it should just be in visibility not in the visibility.) What follows the comma is called an appositive, a noun phrase that clarifies the noun or noun phrase immediately before it. (in this case visibility.) Your use is normal and common. It's a regular grammatical technique. Anybody advising against it is just stating a personal opinion. (As is anybody arguing in favour if it.) It's entirely a matter of style and its use is up to you. Commented Oct 17, 2019 at 2:44

1 Answer 1


It is grammatical, but, as R Sole said, wordy. Moreover, I doubt it says what you mean. I suspect that you want to say that you are using "visibility" in a scientific sense, that "visibility" is decreasing, and that pollution is one cause of the decrease. The proposition that "visibility" is decreasing due to pollution may be implied, but it is not explicitly stated. It requires great care to be clear and avoid verbosity when trying to express three thoughts in a single sentence. Assuming I understand what you mean, try:

"Visibility," as defined by meteorologists, has decreased annually by 1% in the city, in part because of atmospheric pollution."

That is 19 words to express those three thoughts explicitly instead of 25 words to express two thoughts explicitly and imply a third.

Of course, this will not do if that is not your intended meaning.

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