Unusual plurals

As a general rule, we never use an apostrophe in writing plural forms. (A plural form is one that denotes more than one of something.) Hence the things that those shops are selling are pizzas, videos, fine wines, cream teas and mountain bikes. It is absolutely wrong to write *pizza's, *video's, *fine wine's, *cream tea's and *mountain bike's if you merely want to talk about more than one pizza or video or whatever. The same goes even when you want to pluralize a proper name:

She's trying to keep up with the Joneses.

There are four Steves and three Julies in my class.

Several of the Eleanor Crosses are still standing today.

Do not write things like *Jones's, *Steve's, *Julie's or *Eleanor Cross's if you are merely talking about more than one person or thing with that name.

In British usage, we do not use an apostrophe in pluralizing dates:

This research was carried out in the 1970s.

American usage, however, does put an apostrophe here:

(A) This research was carried out in the 1970's.

You should not adopt this practice unless you are specifically writing for an American audience.

In writing the plurals of numbers, usage varies. Both of the following may be encountered:

If you're sending mail to the Continent, it's advisable to use continental 1s and 7s in the address.

If you're sending mail to the Continent, it's advisable to use continental 1's and 7's in the address.

Here, the first form is admittedly a little hard on the eye, and the apostrophes may make your sentence clearer. In most cases, though, you can avoid the problem entirely simply by writing out the numerals:

If you're sending mail to the Continent, it's advisable to use continental ones and sevens in the address.

An apostrophe is indispensable, however, in the rare case in which you need to pluralize a letter of the alphabet or some other unusual form which would become unrecognizable with a plural ending stuck on it:

Mind your p's and q's.

How many s's are there in Mississippi?

It is very bad style to spatter e.g.'s and i.e.'s through your writing.

Without the apostrophes, these would be unreadable. So, when you have to pluralize an orthographically unusual form, use an apostrophe if it seems to be essential for clarity, but don't use one if the written form is perfectly clear without it. (Note that I have italicized these odd forms; this is a very good practice if you can produce italics.)

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