An apostrophe is used in a possessive form, like Esther's family or Janet's cigarettes, and this is the use of the apostrophe which causes most of the trouble. The basic rule is simple enough: a possessive form is spelled with 's at the end. Hence:

Lisa's essay
England's navy
my brother's girlfriend
Wittgenstein's last book
children's shoes
women's clothing
the aircraft's black box
somebody's umbrella
a week's work
my money's worth

This rule applies in most cases even with a name ending in s:

Thomas's job
the bus's arrival
James's fiancée
Steve Davis's victory

There are three types of exception. First, a plural noun which already ends in s takes only a following apostrophe:

the girls' excitement
my parents' wedding
both players' injuries
the Klingons' attack
the ladies' room
two weeks' work

This is reasonable. We don't pronounce these words with two esses, and so we don't write two esses: nobody says *the girls's excitement. But note that plurals that don't end in s take the ordinary form: see the cases of children and women above.

Second, a name ending in s takes only an apostrophe if the possessive form is not pronounced with an extra s. Hence:

Socrates' philosophy
Saint Saens' music
Ulysses' companions
Aristophanes' plays

Same reason: we don't say *Ulysses's companions, and so we don't write the extra s.

The final class of exceptions is pronouns. Note the following:

He lost his book.
Which seats are ours?
The bull lowered its head.
Whose are these spectacles?

Note in particular the spelling of possessive its. This word never takes an apostrophe:

*The bull lowered it's head.

This is wrong, wrong, wrong — but it is one of the commonest of all punctuation errors. I have even met teachers of English who get this wrong. The conventional spelling its is no doubt totally illogical, but it's nonetheless conventional, and spelling the possessive as it's will cause many readers to turn up their noses at you. The mistake is very conspicuous, but fortunately it's also easy to fix — there's only one word — so learn the standard spelling. (There is an English word spelled it's, of course, and indeed I've just used it in the preceding sentence, but this is not a possessive: it's the contracted form of it is or of it has. And there is no English word spelled *its' — this is another common error for its.)

The same goes for possessive whose: this cannot be spelled as *who's, though again there is a word who's, a contraction of who is or of who has, as in Who's your friend? or Who's got a corkscrew?

Note, however, that the indefinite pronoun one forms an ordinary possessive one's, as in One must choose one's words carefully.

There is a further point about writing possessives: when you add an apostrophe-s or an apostrophe alone to form a possessive, the thing that comes before the apostrophe must be a real English word, and it must also be the right English word. Thus, for example, something like *ladie's shoes is impossible, because there is no such word as *ladie. Moreover, a department in a shoeshop could not be called *lady's shoes, because what the shop is selling is shoes for ladies, and not *shoes for lady, which is meaningless. The correct form is ladies' shoes. (Compare that lady's shoes, which is fine.)

Finally, while we're discussing clothing departments, observe that there is at least one irritating exception: though we write men's clothing, as usual, we write menswear as a single word, with no apostrophe. By historical accident, this has come to be regarded as a single word in English. But just this one: we do not write *womenswear or *childrenswear. Sorry.

Copyright © Larry Trask, 1997

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