Commas: They're Not Just For English Majors Anymore. commas with...
Non-Restrictive Elements

By "non-restrictive element" I mean items such as transitional words, direct address, appositives, or others that you could take out and not change a sentence's meaning.

You're probably already familiar with such elements, sometimes called "non-essential" elements. Again, for our purposes, an "NRE" is any element that is unessential to the basic meaning of the sentence.

What you probably haven't realized before is that non-restrictive elements are a lot like introductory elements--they add extra information--but they come in the middle or at the end of a sentence rather than at the beginning.  Also like introductory elements, they can be a single word, like a transition.

The problem with the furniture, however, is that it's on fire.
Here the word however acts as a non-restrictive element. The term "non-restrictive" refers to elements that do not "restrict" the meaning of the sentence. More specifically, they generally do not change the meaning of the subject:
The poem, written in some language I couldn't understand, made me want to throw my book away.
As with introductory elements, the trick to recognizing non-restrictive elements is to find the sentence's main idea. In this case, it's
The poem... made me want to throw my book away.
"Written in a language I couldn't understand" is a non-restrictive element because it merely gives us more information without "restricting" the meaning of the sentence's subject, "poem."

Q. How can I tell whethen element is restrictive or non-restrictive? 

A. Good question.  Here's an opportunity to see how commas can be used to help your reader understand your meaning. Restrictive elements, as you've probably guessed by now, restrict the meaning of a sentence. Consider how the presence of commas can change the meaning of a sentence.

    Lonely people who don't shower often have few friends.
Ask yourself about the meaning of this sentence.  As the sentence is punctuated now, which lonely people have few friends?

The ones who don't shower. The clause isn't set off with commas; that means it restricts the meaning of "lonely people" to ONLY those who don't shower.

Now see what happens if commas are placed around the clause. What does this sentence mean? Which lonely people have few friends?

    Lonely people, who don't shower, often have few friends.
This sentence proclaims that ALL lonely people have few friends (it also implies that none of them showers, a grim thought indeed).  In other words, placing commas around the clause "who don't shower" makes it non-restrictive. That means it doesn't restrict the meaning of the subject, "lonely people."  The fact that they don't shower is just extra information.

Here's another example:

    Presidents, who drive drunk, should never be re-elected.
Which presidents does this sentence say should never be re-elected? All of them. The commas mean that the clause "who drive drunk" is non-essential information and that it does not restrict your re-election policy.

Again, if we remove the commas, we restrict the meaning of "Presidents" to ONLY those who drive drunk.

    Presidents who drive drunk should never be re-elected.
next (review)

Intro, Get Started, IE, CE, 2IC, FANBOYS, CA, NRE, Review

IE: Introductory Elements

CE: Contrasting Elements

2IC: Two Independent Clauses

CA: Compound or Coordinate Adjectives

NRE: Non-Restrictive Elements

A Few Other Situations (quotations, lists, etc.)