Dogs are usually friendly; however, while eating some are unpredictable.

Does "eating" need to be followed by a comma? It appears to me that a comma is necessary because "while eating" functions as a subordinating conjunction, but I want to be 100% certain.

  • 1
    I'm not sure of the grammatical rules behind it, but I would definitely place a comma there in order to prevent the reader's eye from taking "some" as the object of "eating" (viz. "while eating some [dogs]") before moving on to "are unpredictable." The sentence is clearer with the comma, and the comma also prevents a momentarily gruesome image. – Annick Sep 6 '13 at 2:34
  • Hahahaha good point. – 12esonance Sep 6 '13 at 2:49

As I thought, the correct sentence was:

Dogs are usually friendly; however, while eating, some are unpredictable.

See http://www.chompchomp.com/terms/conjunctiveadverb.htm for more on conjunctive adverbs.


The conjunctive adverb ‘however’ is really completely irrelevant here.

The relevant issue is that “while X-ing” acts as a sentence adverb, and sentence adverbs are (almost) invariably followed by a comma. If we recast the sentence to move the conjunctive adverb away from the start of the sentence, a comma is still preferable:

Dogs are usually friendly. While eating, some are unpredictable, however.

In certain cases, the comma may even disambiguate an otherwise ambiguous sentence (as pointed out by Annick—note that I have no idea if the following are anatomically correct or not):

While eating, the brain speeds up your metabolism.
While eating the brain speeds up your metabolism(, eating the tongue does not).

The latter means something entirely different from the former!


Firstly, the use of the semicolon is wrong because however is a conjunctive adverb.

Personally I would change the order for clarity so the sentence becomes:

Dogs are usually friendly, however some are unpredictable when eating.

This order makes the meaning clear because the dog's disposition is the subject of the sentence and this order emphasises that fact. The 'when eating' is an additional condition and thus should be kept at the end to improve clarity.

Note that although people tend to pause after words like 'however' for effect, this is usually only the case in everyday speech and character speech in story writing. I'm not sure about the rules for when a character is narrating the story, but as a rule of thumb I would say only put a comma after however if you purposely want your readers to pause for effect, thus its usage should be few and far between (except in the case of actual audible speech from the characters).

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    I disagree that the semi-colon is wrong, and would argue that your comma is wrong. The clauses either side of the comma can stand alone as separate sentences, hence the minimum break should be a semi-colon. – TrevorD Sep 6 '13 at 10:45
  • Semicolons should not be used with conjunctions and however is a conjunctive verb. (theoatmeal.com/comics/semicolon) If you don't like my answer, write your own. – Pharap Sep 6 '13 at 18:37
  • -1. A conjunction is not the same as a conjunctive adverb. The semicolon before ‘however’ is perfectly fine and standard (see also 12esonance’s link), and there is no reason (apart from varying your style) that ‘when eating’ should not start the clause. – Janus Bahs Jacquet Sep 8 '13 at 12:12

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