The apostrophe either is prohibited from doing its work or is expected to work where it’s not supposed to. What an apostrophe does is not all that complicated. Heck! It’s not like an apostrophe is a comma, y’know.
An apostrophe really only does two things: stands in for letters in a contraction or shows possession.
Standing in for Those Not There
Folks, contractions are easy! It + is = It’s; would + not = wouldn’t; there + is =there’s. Get it? Simple, right? If it is so simple, why do we see the apostrophe left out all over the place? How many times do we see Im, theres, wont, til (which should be ’til for until), or the one that tends to set my teeth on edge most which should be ’most because people mean almost?
And folks, if you want to shorten the 1960s, it is the ’60s. Please notice that there is no apostrophe in the whole numerical decade and the apostrophe appears before the shortened number to stand in for those that are missing.
Helping Show Who Owns What
It’s bad enough that the apostrophe is prevented from its proper place in contractions, it often gets barred from doing its job with possessives. Admittedly, showing possession with an apostrophe is a little trickier than contractions, but it’s still pretty logical.
If you are showing that something owns (possesses) something and the word does not end in an s, put in an apostrophe and an s: boy’s, girl’s, children’s, geese’s. Yet how many restaurants, bars, or taverns have doors posted womens and mens?
If a singular word ends in an s, put an apostrophe then an s: boss’s, James’s, lass’s.
Just tack on an apostrophe to plural words that end in s to show that they all own something: bosses’ desks, boys’ bikes, students’ grades, writers’ books.
(Psst! Never use an apostrophe with a possessive pronoun. That includes its –the dog gnawed its bone.)
Apostrophes Against Plurals
There is a tendency for people to force apostrophes into servitude to indicate the plural, especially with abbreviations and acronyms. There is no need! Write assts., mgrs., CDs, and apps. This also applies to numbers and symbols: 3s, 13s, $s, or &s.
The only time an apostrophe should be used to show something is plural is for lowercase letters; p’s, q’s, and g’s. In this case, the apostrophe is needed for visual separation. Otherwise, don’t do it!
The OWL, Purdue’s Online Writing Lab, has a very nice page on how to properly use apostrophes.
“But, really, how big a problem is this?” you ask.
Well, there is a subversive group of grammar aficionados who go around correcting apostrophe abuse and misuse on signs. In fact, there were a couple of gentlemen who corrected a sign at a national forest and were arrested for vandalism.
So, if you can’t use apostrophes correctly for the apostrophes’ sake, do it to save a radical grammarian!
Image taken from http://blackcatsramblings.info/damn-that-apostrophe