The Chicago Manual of Style says

A phrase that is restrictive—that is, essential to the meaning (and often the identity) of the noun it belongs to—should not be set off by commas.

What sort of phrases cannot be restrictive or non-restrictive? What about the following, is 'rusted' non-restrictive?

  • Your car, rusted, looks ugly

I don't think so, because it seems to me to change the meaning of the predicate, that your car looks ugly as it is rusted. Why is the sentence not grammatical?

  • In that example, "rusted" isn't being used restrictive or non-restrictively. "Looks" is being used as a linking verb, much like "is" or "seems," and "rusted" is the predicate adjective. It doesn't mean, "Your rusty car looks ugly." It means, "Your car looks ugly (now that it has) rusted."
    – Billy
    Aug 22 '18 at 19:43
  • I only understood your comment from the second sentence @Billy
    – user99677
    Aug 22 '18 at 19:54

Your sentence is grammatical.

In your sentence, rusted is parenthetically nonessential information.

In other words, the sentence could be rephrased in this way:

Your car (which happens to be rusted) looks ugly.


Your car looks ugly. It's also rusted.

In other words, rusted is non-restrictive. It, along with the pair of commas, can be removed without impacting the essential meaning of the sentence itself.

If rusted were essential to the sentence, then it should not be provided within comma pairs:

Your rusted car looks ugly.
Your car looks ugly because it's rusted.
Rust is making your car look ugly.

I am not aware of any phrase that is neither restrictive nor non-restrictive. Either the phrase plays an essential role to the text that surrounds it or it doesn't . . .

  • are all non-restrictive parenthetical??
    – user99677
    Aug 22 '18 at 23:42
  • @user3293056 Almost always. However, it's possible (in some constructions that are unusual) to use a non-restrictive without parenthetical punctuation if the sentence is short enough and the meaning is clear: Her words went of course unheeded. Normally, there would be a pair of commas around of course. But there doesn't have to be in order for it to be understood. It would an uncommon style decision to exclude the pair of commas—but a style decision nonetheless. Aug 23 '18 at 0:56
  • @user3293056 I just thought of a different circumstance of a non-restrictive that is not parenthetical at all. I had been in a mindset to consider something that came in the middle of a sentence—but a non-restrictive phrase can also come at the end of a sentence after a single comma: I had to fix my printer, which I bought less than a year ago. Here, the second part of the sentence is non-restrictive but not parenthetical. Aug 23 '18 at 1:04

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