Parentheses and how to nest them ([{}])

In Tips & Tricks by Kali Tal

A parenthesis contains a comment that, while pertinent, interrupts the flow of the sentence or paragraph.  If a sentence is well-formed, text in parentheses can be removed without changing the meaning of the sentence.  Let’s look at a few examples.

I put on a sweater (red, because that’s my favorite color) and went to the party.

I said hello to Clyde and smiled sweetly (even though I hate him).

These are simple sentences and allow you to easily see what parentheses do:  they allow a level of metacomment, so that the content of the “real” sentence is contextualized or supplemented, or even sometimes contradicted by what’s in the parenthesis.  Stage actors do this when they briefly break character and whisper comments about other characters, or about the play, to the audience.  Such speech is called an aside, and that’s what parentheses create.

In scientific writing, parentheses usually inclose information that is useful or necessary to the reader, so that the information is available but does not break the flow of the scientific narrative.  They often enclose citations (Tal, 2013), and to set measurements (25% of the time)  off from the rest of the text.  Let’s take this paragraph as an example:

We sent a questionnaire to former patients aged >18 years and resident in Switzerland. Three hundred participants (58% of 514 eligible) returned the questionnaire (mean age 23 years, 56%  were female; 44% had isolated growth hormone deficiency (IGHD) or idiopathic short stature (ISS), 42% with associated diseases or syndromes, 14% after childhood cancer).

Because English readers understand that parentheses contain asides, it’s confusing to come across two opening parenthesis in a row (like this! (and like this!)). So the convention in English is to nest parenthesis.  Here are the rules:

The (…) goes on the outside.

The first nesting uses a square bracket:  (…[…]…).

The second nesting (which I hope you never need to use) is (…[…{…}…]…).

So the corrected paragraph looks like this:

We sent a questionnaire to former patients aged >18 years and resident in Switzerland. Three hundred participants (58% of 514 eligible) returned the questionnaire (mean age 23 years, 56%  were female; 44% had isolated growth hormone deficiency [IGHD] or idiopathic short stature [ISS], 42% with associated diseases or syndromes, 14% after childhood cancer).