I have come across the following sentence in Advanced Grammar in Use by Martin Hewings (Unit 100 Inversion (2))

So dangerous did weather conditions become, that all mountain roads were closed.

I'm wondering whether the comma is not a mistake here.

A similar sentence without inversion would read

Weather conditions were so dangerous that all mountain roads were closed.

What say you?

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    If there was no comma, I might misread it as "become that", instead of "so ... that". – Damkerng T. Nov 28 '13 at 9:44
  • But that wouldn't change the meaning of the sentence, would it? – mick Nov 28 '13 at 10:02
  • The two sentences have the same meaning, at least to me. But without that comma, how should I put it?, can be quite confusing. Definitely a bad style, but I'm not sure to say whether it is wrong or not. – Damkerng T. Nov 28 '13 at 10:09
  • I'm with Damkerng T on this; commas are here to serve, not dictate. I'd put the comma in if using the OP's rather nice ordering (and have *'authorities' to counter those some prescriptivists would say show it's ungrammatical). The comma makes reading easier (avoiding any hint of garden-pathness) and causes no problems except to sensitivities. *'Sometimes, there is no grammatical rule that dictates the use of a comma in a particular spot within a sentence, but the use of one, creating a pause, can [be useful].' *'Commas: Use commas to create a pause if your breath units are getting too long.' – Edwin Ashworth Nov 28 '13 at 10:12
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    I have just found a similar sentence in Practical English Usage (3rd edition) by Michael Swan. However, there is no comma. So ridiculous did she look that everybody burst out laughing. (p 280) – mick Nov 28 '13 at 10:19

Here is a perhaps more convincing authority recommending

Using Commas to Prevent Misunderstanding:

Sometimes you must use a comma to make the reader pause in the appropriate place in the sentence in order to prevent misreading.

Becoming a good writer means developing an awareness of how your sentences will sound to the reader. Reading your work aloud, to yourself or to a friend, is a good way to identify the places in the sentence where pauses--or commas--are needed.

Example 1:

Without comma: Before leaving the soldiers demolished the fort.

A comma is needed here to prevent [an initial] confusion in interpreting the sentence. Without the comma, the reader might [at first sight] think that the soldiers were being left, rather than doing the leaving. The sentence might have gone on to end this way: "Before leaving the soldiers, I kissed them all goodbye".

With comma: Before leaving, the soldiers demolished the fort.

  • 2
    I love the explanation, but I think that the example sentence with 'before leaving the soldiers' is different to the one I used. – mick Nov 28 '13 at 11:28
  • Original) So dangerous did weather conditions become, that all mountain roads were closed.


So, a normalized version could be:

  • 1.) Weather conditions became so dangerous [that all mountain roads were closed].

And that seems fine to me, as it is, without the comma. Note that the content clause "that all mountain roads were closed" is licensed by the adverb "so".

With the insertion of the comma:

  • 2.) Weather conditions became so dangerous, that all mountain roads were closed.

To many, a comma probably isn't acceptable here -- or at least, the preference would be for no comma.

When the matrix clause is inverted:

  • 3.) So dangerous did weather conditions become that all mountain roads were closed.

and that seems fine too (without the comma).

If the comma is now inserted, then we get the OP's original example:

  • 4.) So dangerous did weather conditions become, that all mountain roads were closed.

In this version, the comma doesn't seem to be so bad, imo -- that is, it seems to be okay or fine. The comma being acceptable in this version might be due to the presence of the inversion in the matrix clause, and/or due to poetic license by the writer.

Just some thoughts . . .


In the given example, "that" introduces a defining clause. A defining-relative clause is necessary to the meaning of the entire sentence and for that reason is not set off by a comma. "So dangerous did weather conditions become" cannot stand on its own as an independent clause. It needs "that all mountain roads were closed" for there to be any sense to the thought. Michael Swan is a respected authority on English grammar. If he doesn't put a comma before "that" in this context, as mick pointed out, then I'd go with him.

  • That was my thought too. We don't put commas before that in defining relative clauses. – mick Jan 27 '14 at 11:37

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