Apostrophes pretty much have two uses: making a contraction or making a possessive. Possessive apostrophes are the ones I see misused the most, so they’ll be the ones we look at in this post.
When do you use it?
The classic Elements of Style (better known as Strunk & White) starts off with this advice: “Form the possessive singular of nouns by adding ‘s.” Yes, even for singular nouns ending in s.
You also use an ‘s with a plural noun that does not end in s. Example: men’s room, women’s room. Plural nouns that end in s just get an apostrophe to the end of the word. Example: kids’ rooms. (Yes, I’m feeling particularly creative with these examples.)
But it is singular, and it’s isn’t the possessive!
Yes, that’s right. Possessive pronouns like his, hers, its, yours, ours, and theirs do not use apostrophes.
It’s = it is. If you’re unsure of which one you’re supposed to use, read your sentence aloud and replace it’s with it is. If it sounds right, you use it’s. If not, you’ll use its.
What about proper singular nouns that end in s? Don’t you just use only an apostrophe then?
The AP Stylebook (at least the version I have, published in 2002) is where I find the rule that singular proper nouns ending in s should get the apostrophe-only treatment.
However, Strunk & White disagree (see above), as does Roy Peter Clark, author of The Glamour of Grammar, though both allow that there are exceptions.
Clark advises you to “let your ear help govern the possessive apostrophe.” He says to use ‘s for all singular nouns that end in s, but listen to the words to gauge whether it’s an exception to that rule:
There are classic examples when adding an s gives you that Velcro feeling: I would not say Achilles’s heel. Achilles’ will do fine, thank you, with the prepositional phrase a convenient escape hatch: the teachings of Socrates.
However, Clark also says that generally, most proper singular nouns sound right with the ‘s added, like using “James’s book” instead of “James’ book,” despite what the AP Stylebook says:
The [AP] stylebook justifies the missing s based on the value of ‘consistency and ease in remembering a rule.’ To which I respond: What about the needs and experiences of the reader?
Most language experts advise writers to ignore restrictions that require you to write or say something awkward or ugly, especially something that offends the ear. In this case, let us match punctuation to speech. As long as the snake isn’t swallowing its tongue, let the reptile hiss.
On a final note:
Apostrophes do not make plurals. Apostrophes do not make plurals. APOSTROPHES DO NOT MAKE PLURALS.
The only exception to that rule I’ve ever seen has been when discussing the plural of a single letter, where not using an apostrophe could cause confusion. Example: “She had all A’s on her report card.” versus “She had all As on her report card.”
Other than that? Apostrophes do not make plurals.
All are Amazon links (though not affiliate links).
The Elements of Style, Fourth Edition by William Strunk, Jr. and E.B. White
The Associated Press Stylebook
The Glamour of Grammar by Roy Peter Clark