A nonessential element, also referred to as nonrestrictive element, is a word, phrase or clause that is not essential to the meaning of the sentence. When a nonessential clause is removed from the sentence, the sentence still makes sense without it; it is unrestricted, or not essential. These elements are essentially a bonus; they provide extra, although unnecessary, information to the sentence.
Nonessential elements are always offset with commas. The commas dictate a pause when you are reading the sentence or speaking it out loud. If the word, phrase or clause is easily removed from the sentence or moved to another spot within the sentence, the clause is set off with commas on each side. Likewise, if the element interrupts the flow of the sentence, offsetting commas are used.
“However” is a nonessential word because it interrupts the flow of the sentence, requiring offsetting commas. It is also moved without changing the meaning of the sentence.
“Her coworker” is a nonessential phrase because it has a noun but no subject of a verb and is not necessary for the sentence to retain its meaning. That Sammie is her coworker is just bonus information.
“Who was quite beautiful” is a nonessential clause because it has a subject and a verb and is not required to stay in the sentence for it to make sense. That the girl was beautiful is just extra information.
Nonessential elements sometimes appear at the end of sentence; this is okay. To correctly use commas in this case, you must use one offsetting comma and follow the nonessential element with the proper punctuation to end the sentence. Use the same principles to determine if the word, phrase or clause is necessary for the sentence to retain its meaning as you do for those elements that appear in the middle of a sentence.
Sometimes, what might appear as nonessential is actually a descriptive adjective, making it essential to the meaning of the sentence. For this reason, it is important to clearly understand the intent of the intended message of the sentence. Consider the following examples:
Example 1: Sarah and daughter Jane had dinner last night.
Example 2: Sarah and her daughter, Jane, had dinner last night.
In the first example, “daughter” is a descriptive adjective and essential to the sentence. In the second example, however, “Jane” is a nonessential word because it is not necessary to maintain the sentence’s meaning.