Double parenthesis in academic writing [duplicate]

Question

I have the following question. I have a text in which I want to insert a small mathematical formulation, namely between parenthesis. Unfortunately, this mathematical formulation also contains a parenthesis, which would result in a double parenthesis in the text. Is this allowed in academic writing or do I have to formulate it differently? My text looks like this, for example.

This leads to a function (f(x)), which then...

Answer 1

Is this allowed in academic writing or do I have to formulate it differently?

There is no Central Committee for Academic Writing issuing decisions on which things are Allowed and which are Not Allowed, so it does not make a lot of sense to formulate the question this way. There are just people with various opinions on what constitutes good writing, with near consensus on some things and violent disagreement on others. So it is really up to you to figure out which principles you want to follow when it comes to parentheses etc.

Accordingly, the question is not can I do this? (yes, you can), it is should I do this? As you yourself have noticed, two consecutive parentheses look a bit awkward, so if there is an obvious way to avoid them, I would say it is probably for the best to do so. For example, you can instead write

This leads to a function f(x), which then ...

This leads to a function f(x). The function f(x) then ...

This leads to a function, which we will call f(x). The function f(x) then ...

This leads to a function, f(x), which then ...

This leads to a function – f(x) – which then ...

or any of a number of other possibilities. If you want to write mathematics well, I recommend that you invest some time into thinking about various different ways you can formulate sentences like this. After some practice your brain will automatically start coming up with a number of alternative ways of phrasing any given sentence, which will pay off handsomely when it comes to avoiding issues of this sort.

Answer 2

In the example you mention there is little reason to enclose f(x) within parentheses in the first place. As pointed out in the comments and another answer, writing, for example,

This leads to a function, f(x), which then ...

is likely preferable.

In other cases, I tend to follow the recommendation outlined in the Physical Review Style and Notation Guide, namely

Square brackets enclose a phrase that already contains parentheses.

Form:

Recall that the Brown-Green theory [see Eq. (2)] is still to be . . .

In my opinion, ending with ")]" looks less awkward than "))" and keeps the syntactical meaning of each bracket clear. Of course, depending on where you're publishing another style guide may dictate another solution.

Answer 3

In general there is nothing wrong with having a math expression inside a parenthetical comment, even if that math expression itself uses parentheses. So something like "a periodic function (for example, sin(x))" would be fine.

However, I would consider it a bad idea for the math expression to be the only thing inside the parentheses, as in your example, since it creates confusion about whether the outer parentheses are part of the math expression (which can change the meaning). This applies even if there are no inner parentheses.

Answer 4

This is generally permissible. However, consider also adding spaces between the outer parentheses and the inner content, especially if you can use thin spaces or hair spaces. This increases legibility.

Answer 5

I completely agree with the other answers suggesting using commas or other approaches, but if you really want the parentheses, a simple trick to make them look a bit clearer is to use a different font for the f(x), just as I did here. Use a monospaced font for them and that should allow your reader to easily distinguish between the parentheses that are part of the text and those that are part of the mathematical notation. Something like this in LaTeX:

\documentclass{article}
\begin{document}

This leads to a function (\texttt{f(x)}), which then ...

\end{document}

Which looks like this:

The change in font, especially to a monospaced font which we are used to seeing used for code in technical documentation, makes it easy for the eye to separate the outer and inner parentheses.