Part I We are all familiar with the two curved marks that we know as the parenthesis ( ), but what some of us may not know is that in English grammar, the parenthesis is actually any amplifying or explanatory word, phrase, or sentence that’s set off from a sentence or passage by some form of punctuation. That punctuation can be those two curved marks (they are called
brackets in British grammar), of course, but depending on the importance of the inserted information and the writer’s intention, it can also be a pair of enclosing commas or a pair of enclosing dashes.
Let’s take a look at the following examples:
(1)
Parenthesis by comma: (a) “Ferdinand Magellan, who claimed the Philippine islands for the Spanish crown in 1521, was actually a Portuguese whose native name was Fernão Magalhães.” (b) “Cleopatra, the legendary queen of Egypt from 51 B.C. until her suicide by asp bite 21 years later, greatly influenced the affairs of the Roman Empire.”
(2)
Parenthesis by dashes: “Their kindly uncle was terminally ill—they said they didn’t know it then—but his nephews and nieces just went on their merry ways.”
(3)
Parenthesis by parentheses: “While I was driving it out of the used-car dealer’s yard, the nicely refurbished 1994 sedan (the dealer assured me its engine had just been overhauled) busted one of its pistons.”
In each of the three examples above, the information set off by the punctuation marks—whether by commas, dashes, or parentheses—is called a
parenthetical, and its distinguishing characteristic is that the sentence remains grammatically and semantically correct even without it. A parenthetical is basically added information; however, it isn’t necessarily optional or semantically expendable. It may be needed to put the statement in a desired context, to establish the logic of the sentence, or to convey a particular tone or mood for the statement. In fact, the punctuation chosen for a parenthetical largely determines its optionality or importance to the statement.
So the big question about parentheticals is really this: Under what circumstances do we use commas, dashes, or parentheses to punctuate or set off a parenthetical from a sentence?
In Example 1(a) above, the parenthetical “who claimed the Philippine islands for the Spanish crown in 1521” is what’s known as a nonrestrictive relative clause. A
nonrestrictive relative clause is a parenthetical that provides information that’s not absolutely needed to understand the sentence; in other words, it is
nondefining information. The sentence will remain grammatically and semantically intact without it: “Ferdinand Magellan was actually a Portuguese whose native name was Fernão Magalhães.” Without the nonrestrictive relative clause, however, the sentence loses a lot of valuable information about its subject, “Ferdinand Magellan”; in fact, the intended context for the statement disappears completely.
For such type of parenthetical, the most appropriate choice of punctuation is a pair of enclosing commas, as was used in the original sentence. It won’t do to punctuate a nonrestrictive relative clause with dashes or parentheses, for either of them would render the information optional, as we can see in these two versions of that sentence: “Ferdinand Magellan—who claimed the Philippine islands for the Spanish crown in 1521—was actually a Portuguese whose native name was Fernão Magalhães.” “Ferdinand Magellan (who claimed the Philippine islands for the Spanish crown in 1521) was actually a Portuguese whose native name was Fernão Magalhães.” Both of these sentence constructions run counter to the writer’s original intention.
We must keep in mind, though, that the same parenthetical—“who claimed the Philippine islands for the Spanish crown in 1521”—would have become a
restrictive relative clause had the subject been a generic noun like, say, “the explorer,” in which case the pair of enclosing commas would have been rendered unnecessary: “The explorer who claimed the Philippine islands for the Spanish crown in 1521 was actually a Portuguese whose native name was Fernão Magalhães.”
We will continue this discussion in the next essay. (January 12, 2008)
NOTE: In the essay above, the italicization of the parenthetical in the sentence given as example is done for emphasis only. Parentheticals are normally written or printed in the same Roman typeface as the rest of the sentence.
MORE RECENT REFINEMENT: For greater clarity, the title of the original posting of this essay, "Parenthesis isn’t just optional material or an afterthought," has been changed to "Parenthesis isn’t just those twin curved marks but any amplifying material." Part I of the discussion now also takes note that what's known as "parenthesis" in American English is called "brackets" in British English.
(Jose A. Carillo, August 26, 2022)