A nonrestrictive clause provides additional information about a noun but does not change the fundamental meaning of the sentence. It is typically set off by commas. Here are a couple of examples:
- My brother, who lives in New York, is visiting us next week.
- The car, which I bought last year, has already broken down.
In both examples, the nonrestrictive clauses ("who lives in New York" and "which I bought last year") add more information but are not essential to the main point of the sentences.
If you have specific sentences in mind, I can help you determine whether any of them correctly use a nonrestrictive clause.