Grammar Tips. Comma 17.

Non-restrictive information is set off with a comma when the non-restrictive is found within rather than at the end of the sentence, it should be set up with a pair of commas. When the non-restrictive comes at the end of the sentence, only one comma is needed.

INCORRECT: Robert Moss’s first book Urban Guerillas was published when he was 25.

CORRECT: Robert Moss’s first book, Urban Guerillas, was published when he was 25.

(Robert Moss has only one first book.)

The sentence which was provided is grammatically incorrect and lacks clarity. It seems to be attempting to convey a rule about using commas to set off non-restrictive information within a sentence. However, the structure and wording make it difficult to understand the intended meaning. Here's a revised version of the sentence that clarifies the rule: "When non-restrictive information is found within a sentence, it should be set off with a pair of commas."

Here are a couple of examples illustrating the correct usage:

1. Incorrect: "My friend Tom, who loves sports is always active."

   Correct: "My friend Tom, who loves sports, is always active."

In these examples, the non-restrictive information (the clause "who loves sports") is set off with commas to indicate that it provides additional, non-essential information about the subject.