As a rule, you should not use an apostrophe to make a plural: write apples, not apple's. There are a few exceptions, though, where an apostrophe makes a plural clearer, mainly with single lowercase letters. This article explains when an apostrophe is allowed.
English grammar can be tough, and its many rules and exceptions make it even tougher. Have a look at these two examples:
- Miiko spells her name with two i's.
- Miiko spells her name with two is.
Which sentence is confusing? The second one, right? In the first example, the apostrophe before the s makes it clear that the name "Miiko" contains the ninth letter of the alphabet twice.
So can you use an apostrophe followed by an s to form a plural?
Plurals with apostrophes: it's all about clarity
It turns out that you can, as the two examples above show. With single lowercase letters, an apostrophe is advisable to avoid confusion. Here are two more examples:
- Make sure you dot all the i's and cross all the t's.
- Steve got five A's on his report card.
Capital letters often need no apostrophe (three Bs), but some, such as A's, I's, and U's, would look like other words without it.
Numbers usually need no apostrophe:
- Binary code is written in 1s and 0s.
- The 1970s were wild, or so I was told.
- I miss the Sunday morning cartoons of the '80s.
In the last example, the apostrophe stands in front of the decade, in place of the missing digits 19. It does not make the plural.
If you read an older English guide, you may find that you need an apostrophe to form the plural of numbers, so that you would write 1970's and 80's. Style guides today no longer recommend this.
Some writers also use an apostrophe to make a plural of a word that is not a noun, such as do, if, or but. Style guides disagree here: some write do's and don'ts, others dos and don'ts. Whichever form you choose, use it consistently.
- Everyone should learn the do's and don'ts of small talk.
- I want the job done, no ifs or buts.
Abbreviations that contain periods take an apostrophe in the plural, while abbreviations without periods do not:
- Of the five B.A.'s who applied for the position, only one qualifies.
- Mark says he needs to hire several PhDs for his new startup.
Conclusion
There are some cases where you can use an apostrophe and an s to make a plural, but the general rule is that you shouldn't. All the examples above are exceptions, and like many other exceptions, they are worth memorizing. A sign that reads "Fresh apple's for sale" is still wrong.
The apostrophe has other jobs too, such as showing possession. See how to use apostrophes correctly for all of them. And if all these rules feel overwhelming, check your writing with the Spell Checker: it takes some of the burden of proofreading off your shoulders.