Interrupting a sentence with no punctuation needed

In this series on interruptions in sentences, we have looked at interruptions in parentheses, interruptions with dashes, and interruptions with commas. But it is also possible to interrupt a sentence with no punctuation around the interruption. You do this when the interruption is actually a crucial part of the sentence. In grammar terms, this is called “essential.” These interruptions are “essential” because they help define or identify the exact thing you are talking about. They restrict the discussion to the exact item you mean. Here is an example:

The small arrow on the Styles group title bar opens the Styles pane.

The phrase on the Styles group title bar interrupts between the subject arrow and the verb opens. There is no punctuation surrounding this interruption because it is essential to help the reader find the exact arrow you are talking about out of all the arrows that might exist on a typical computer screen.

The poet Robert Frost wrote “Stopping by Woods on a Snowy Evening.”

Here there are no commas around Frost’s name because his name is essential to the sentence. It identifies which poet you are talking about. Without his name, the reader would have to ask, “Which poet, out of all the poets in the world and throughout history, are you talking about?”

Notice that if you put his name first, there would be no question of who you were talking about, because his name clearly identifies him. In that case any further description, such as the words a 20th-century American poet, would be a nonessential interruption and require commas:

Robert Frost, a 20th-century American poet, wrote “Stopping by Woods on a Snowy Evening.”

Here are some additional examples of interruptions:

1. The book that is in the center of the coffee table is very important to me.

2. World Art: The Essential Illustrated History, which is on the coffee table, is my favorite art book.

In sentence 1, the interruption is essential to identifying the book out of all the books in the world. The essential information cannot be surrounded by commas.

In sentence 2 the book has already been fully identified before the interruption. The interruption merely adds additional description that is not needed for identifying the item. Commas are needed.