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I have one .msi. Then I get another. Do I now have:

two .msis


two .msi's


two '.msi's

or something else?

marked as duplicate by tchrist Jul 26 at 14:39

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  • 1
    You could bypass this altogether and just say "two .msi files". Unless, of course, you have a word/character/space limit. – Pam Jul 26 at 13:47
  • Are you asking about grammar or orthography? Grammar is what you say aloud and hear; orthography is what you write. – tchrist Jul 26 at 13:55
  • @tchrist I disagree with the close vote. They're similar but clearly not identical - a file extension is not necessarily an acronym. txt is short for 'text'. I can even create my own extensions however I want. – Sarov Jul 26 at 19:36

One easy way round it is to write

two .msi files

which also makes it clear to anyone who doesn't know what .msi means.

Another solution is to use uppercase letters for the file extension:

two MSIs
two .MSIs

Its best to avoid the greengrocer's apostrophe.

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