Hello,

This is driving me nuts! How do I write the plural of an acroynm?

Is it PCs or PC's?

I have been told by someone with a degree that you absolutely don't need an apostrophe, however I found a dictionary definition of apostrophe that says it is used for omission of letters from a word, the possessive case, and the plurals of letters, numbers and abbreviations.

Variations with plurals and possession:

One OS (operating system), many OS's.Many OSs? Many OSes?

It is the OS's primary function. (one operating system, posession)

Is is the OSs' primary function. (many operating systems, posession)

Aaargh. Help!