Had a discussion with a colleague on the following sentence today:

By default situation A will happen, unless you choose to activate option B.

I have set the comma as indicated above, but my colleague is convince the comma should be after the "unless".

As a non-native speaker I don't feel I have the authority to overrule my colleague but my gut says the comma should be as indicated above. Can someone help me? Thanks.


The normal usage dictates no comma at all:

By default, situation A will happen unless you choose to activate option B

(the comma after "default" is there because "by default" is an adverbial phrase, and these require a comma if they start a sentence)

Anyway, "unless" here is a dependant word, and as such does not use a comma.

However, in case of a long sentence, you may use a comma to break the sentence into more manageable chunks for easier comprehension:

By default, situation A [, including things D, E and F, as well as potential danger G,] will happen, unless you choose to activate option B [, which will disable things D and F and protect you from G].

  • Hm, would love to see a source for the comma after "default". To me that seems weird. The example is significantly shortened. The original sentence is quite long which is why I'd prefer to insert a comma. Is it wrong to insert a comma, or is it simply optional? (and if it is optional: were do I insert it?)
    – nanos
    Feb 3 '17 at 15:13
  • @nanos "by default" is an adverbial phrase and requires a comma if it is in the beginning of the sentence. For the other thing, I am not 100% sure, but I have seen suggestions to use a comma to break up a long sentence. In that case, it is definitely used before the "unless". I will try to find more information on this. Feb 3 '17 at 15:28
  • 1
    @nanos I have expanded the answer; turns out you can indeed insert an optional comma before "unless" to make it easier to read. Feb 3 '17 at 17:35

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