I understand the "things gathering" example is a way of trying to find a case where you absolutely have to use the plural verb.

Why does the writer use where instead of in which? Shouldn't where be connected with places?

Does it sound fine if I say, "~ to find a case in which you absolutely have to use the plural verb?"

I looked it up in the dictionary. It says where can be used when referring to a particular stage in a process or activity

However, I have come across some articles in which they place where after a noun "that's irrelevant to places." Take the sentence above for an example, the writer uses where to connect the clause with a case, which makes me really confused, because a case in the sentence is neither a place nor a particular stage in the process.

Much obliged for your help.
Hi David,

You will find that, in actual practice, many people use "where" and "in which" interchangeably to refer to circumstances that apply to what's being discussed.

I think you'll find it's similar to using "since" instead of "because." It's not 100% precise, but it's done, and it's understood by other when it is used that way. I do it myself.
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Acoording to what you said, is it ok if I say, "I have come across some articles where they place where after a noun thats irrelevant to places?"
It's certainly a very common use and *I* think it's fine. (I know, I know - "Me and Jim went to the store" is common use, and still utterly WRONG, but I think this "where" usage is okay. Like I said, I do it myself.)

However, if it feels awkward to you and you "notice" every time you type it, then use "in which."