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The NY Times uses both "on Mac OS X" and "in Mac OS X". Can someone explain which one seems more appropriate if there is no difference?

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Can you be more specific? The preposition choice highly depends on the sentence and, more specifically, on the verb used. If you ask for a certain verb, it'd be easier to answer. Related (not sure if they are dupes yet): “on a project” vs “in a project”, “in orbit” vs. “on orbit” – Alenanno Jan 31 '12 at 9:54

To me, at least, "on Mac OS X" refers to things that run on top of Mac OS X, while "in Mac OSX" refers to things that are part of Mac OS X.

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+1. On Mac OS, MS Word does such-and-such. In Mac OS, memory is managed by thus-and-such. – Monica Cellio Jan 31 '12 at 15:36

In computer terminology, "on" typically refers to things that involve a "platform":

I sell my music on Amazon.

My website is on the World Wide Web.

"In" will refer to specific programs, stores or components:

I sell my music in the iTunes store.

To open a file in Excel...

The confusion around Mac OS X is that it qualifies as both a platform and a specific piece of software depending on context:

My application runs on Mac OS X.

To delete a file in Mac OS X...

So the correct answer is that it depends on the specific usage. David Schwartz's answer provides a good rule of thumb for determining which usage is correct in a given scenario.

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@AndrewLeach: Yep, pretty much the same thing I noted here. That question was closed, unfortunately. :P – MrHen Oct 24 '13 at 16:15

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