A new Victoria's Secret ad abuses an apostrophe, but unfortunately, it's a common error. Here's the scoop on when to use apostrophes to make things plural. (Hint: Almost never.)
Do You Ever Use Apostrophes to Make Plurals?
Yesterday, someone on Twitter asked me whether he should use an apostrophe when shortening the word professionals to pros. The short answer is no because although pro is casual, it's recognized as a word in its own right,1, 2 and since it's a regular old noun, you make it plural the same way you'd make any other common noun plural. In this case, just add s—no apostrophe—pros.
The longer answer is that it's not a completely unreasonable question because apostrophes are used to show omission. We use apostrophes in contractions to combine two words and show that we've eliminated some letters (the apostrophe in didn't shows that we've omitted the o in not), and we use apostrophes in rare instances such as rock 'n' roll (to show that we've omitted the a and d in and). Could an apostrophe in pro's show that we're writing professionals without all the letters in between pro and s? Technically, I suppose it could, but that's just not how we do it, particularly because (as I said) pro is considered a word.
Apostrophes Make Single Letters Plural. One rare instance when you use apostrophes to make things plural is in the case of single letters. If you want to write that someone should mind his p's and q's, you use an apostrophe to make p and q plural. Using the apostrophe for single letters is especially helpful when you're writing something that would be mistaken for a word. You want people to know you're talking about i's and u's, not the words is and us. [Note: Guardian style is Ps and Qs.]
Apostrophes Occasionally Make Acronyms and Initialisms Plural. Sometimes people will use an apostrophe to make an initialism such as CDs and RBIs plural, but I don't recommend it. It used to be more common, but style guides moved away from it over the years. I am not aware of any major style guide that still recommends using an apostrophe to make initialisms (without periods) plural, but since The New York Times did it as recently as 2007, it's probably still right to say that it's a style choice—just a rare and unpopular style choice.
When I went to the Victoria's Secret website to get a screenshot of the Body's ad, I actually noticed that they were also using an apostrophe to make an initialism plural. It doesn't seem to be there now, but yesterday, they were promoting PJ's (with an apostrophe). I was surprised that nobody had complained to me about that too because I used to often get complaints about The New York Times doing it when it was their style.
Apostrophes Sometimes Make Numerals Plural. Finally, there is some disagreement about whether to use apostrophes to make numerals plural. Oxford Dictionaries says to write 7's, but The Chicago Manual of Style says to omit the apostrophe and write 7s. I'm more familiar with the no-apostrophe rule, so that's what I use.
Getting back to the Victoria's Secret Body's ad, it may have actually included a punctuation get-out-of-jail-free card.