I'm preparing for academic IELTS by writing some essays and then correcting those using a grammar correction app.

In the following sentence,

In its turn, each gore consists of horizontal segments, or panels.

The app suggests deleting a comma after 'segments', but it feels like it might change the meaning. I meant that 'panels' is another name for 'segments', but without the comma, it's probably possible to conclude that each gore can be made either of segments or from panels.

What is the correct comma usage here?

  • 6
    I agree with you. Always be wary of grammar apps.
    – Peter
    Jun 17, 2021 at 8:44
  • I would suggest that to disambiguate it further you might write horizontal segments or horizaontal panels
    – mdewey
    Jun 17, 2021 at 16:00

4 Answers 4


You should definitely keep the comma, for roughly the reason that you say.

With the comma, your sentence is ambiguous between the intended reading (whereby horizontal segments are called "panels") and an undesired reading (whereby panels are an alternative to horizontal segments, mentioned as an afterthought); without the comma, it would unambiguously have a slightly-different undesired reading (whereby horizontal segments and panels are both possibilities).

Grammar apps are very unreliable, firstly because they don't really understand the text, and secondly because they're often too dogmatic about things that are actually rather nuanced. Even if you did mean "or" in the sense that horizontal segments and panels are both possibilities, the version without the comma would suggest that the two possibilities are on nearly equal footing, whereas the version with the comma would suggest that panels are less common or less recommended or both.

Incidentally, the idiom is "in turn", not "in its turn".


In its turn, each gore consists of horizontal segments, or panels.

As panels is another name for segments, your example is fine. Without that comma, readers may interpret segments and panels as different things.

To get rid of that erroneous comment from the app, you could try

In its turn, each gore consists of horizontal segments, also known as panels.


Put the term panel in parentheses after the term segment.

i.e. horiziontal segments (panels)

  • That does not really help the OP with their dilemma about the comma as it evades the issue. In an exam the OP cannot re-write the rules.
    – mdewey
    Oct 19, 2022 at 14:15

You are correct, there is no definitive rule involving the comma there. However, some academic writing uses different stylizations like this. I wouldn't recommend using it, as without the comma is 100% correct always, regardless of stylization.

  • 2
    What do you mean, "without the comma is 100% correct always"? Are commas never correct anywhere? The OP is not asking about comma usage in general, but about how removing the comma in this context might change the meaning of the sentence to something other than what they intended.
    – gotube
    Jul 2, 2021 at 8:41

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