While in Marks & Spencer's over the weekend, I saw a sign saying
"Women's mac's half price".
My wife thought that there should be an apostrophe in "mac's" as it was plural rather than possessive. I said there should be, as it was an abbreviation of "mackintoshes".
It's wrong, it should be Women's Macs half price. A mac is a mac whether there is one or two. I would be tempted to ask "Mac's what?" You don't put an apostrophe in just to show an abbrevation - even though sometimes it looks awkward, as in CVs.
Equally - and following markrae's post - how often now do you see the old abbrevations with an apostrophe these days, e.g. we spoke on the 'phone, or I came home on the 'bus - you don't/
Quite. It has become the word, still meaning the same as the word it was formally a shortened version of. (Although one has to distinguish between shortened words and genuine abbreviations or acronyms.)
Indeed. As been pointed out, words like bus and phone used to be spelled with apostrophes to indicate missing letters, but now they have become words in their own right, so no apostrophe necessary.
Though actually predates ALthough by about half a millennium in English, being first recorded in the 9th century as opposed to the 14th! It's not an abbreviation.