Comma (and restrictive vs. nonrestrictive clause)

In a previous post, I wrote that using a comma after an introductory dependent clause is standard practice, no thinking required. To refresh your memory, here’s a sentence that begins with an introductory dependent clause:

If you’d like to go to Europe next summer, let’s get together and make some plans!

Things aren’t quite so simple when the dependent clause follows an opening independent clause; in this case, the determining factor for the use of a comma is whether the dependent clause is restrictive or nonrestrictive.

According to the Chicago Manual of Style, a restrictive dependent clause is one that is “essential to the meaning of the main clause.” It shouldn’t be preceded by a comma. Following are two examples:

I’ll attend the conference if you will.  [The restrictive dependent clause is “if you will.”]

Andrew was thrilled when he heard about her new book. [The restrictive dependent clause is “when he heard about her new book.”]

On the other hand, says Chicago, a nonrestrictive dependent clause “is merely supplementary” and should be preceded by a comma:

I have already made my reservation, if that interests you.  [The nonrestrictive dependent clause is “if that interests you.”]

People whose thoughts are mostly positive are happier than people whose thoughts are mostly negative, if you want my opinion.  [The nonrestrictive dependent clause is “if you want my opinion.”]

But what if you really can’t tell if a dependent clause is restrictive or nonrestrictive? In that case,  Chicago advises using the comma.


Tara Treasurefield
Tara’s Writing Studio


About 123clear

I translate foggy information into plain English.
This entry was posted in Blogroll, clause, comma, dependent, independent, punctuation, sentence structure. Bookmark the permalink.

One Response to Comma (and restrictive vs. nonrestrictive clause)

  1. This reminds me of this joke from Demetri Martin:

    “I went to a clothing store. There was a girl there, helping me. I picked some clothes and she pointed me to the dressing room. She said, “if you need anything, my name is Jill.” “That’s amazing”, I thought, “I never met a girl with a conditional identity before. What if I don’t need help?” “Then it’s Eugene.””

    I guess that if she would have reversed the order of her clauses, her conditional identity could be caused by omitting a comma!

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