a. I talked to the man known around here as 'Tall Bobby' who is the mayor of the town.

If there is only one man known around here as 'Tall Bobby', don't we have to have a comma before 'who'?

b. I was in the department known as Boyer that has a flourishing mining industry.

Do we need to replace that with 'which' and have a comma before 'which'?

c. I was in the department that has a flourishing mining industry known as Boyer.

Could this sentence be used if the department is known as Boyer?

This is a question regarding restrictive and non-restrictive clauses. If there is only one 'Tall Bobby', then the clause following it should be non-restrictive. We are giving more information about a person that has already been identified. But since things are clear, is the comma absolutely necessary?

Same question about (b). One could maybe consider (b) as a transformation of (c).

As for (c), I'd say that the sentence works. Nobody would think that the 'flourishing mining industry' is know as Boyer. But maybe that is the only way the sentence can be read according to the rules of grammar. I don't think so.

  • 1
    The first two should be non-restrictive. The third one is ambiguous. Are these sentences you wrote yourself, or ones "found in the wild"?
    – gotube
    May 29, 2022 at 15:17
  • Thank you so much Gotube. I made them up myself.
    – azz
    May 30, 2022 at 6:55

1 Answer 1


Interesting question!

A and B should both have commas, but you're right that since it's so clear that the referent is unique, the commas don't clarify anything. Often enough, native speakers who don't know these rules leave the commas out because in normal rapid speech, we don't bother pausing. To someone familiar with the rule, your writing will look wrong.

Further, a reader who is familiar with the rules about commas might realize it's a non-restrictive clause but that there's no comma, and so go back and re-read it to make sure they hadn't misread.

So, while the comma doesn't contribute to either the meaning or pronunciation of the sentence, for the sake of readability and credibility, you should include the comma.

Sentence C is no good as is because it's ambiguous whether the department or the industry is called "Boyer". If, as you suggest, the department is named Boyer, I can only think of one way to fix it following the comma rules:

I was in the department known as Boyer, which has a flourishing mining industry.

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