There is uncertainty in how the apostrophe fits in with plurals as it has become so comfortable around the letter s since it first started being used at the end of English words in the 16th century.
The apostrophe will dangle off the edge of the plural noun, after the s, to try and avoid confusion with the singular version.
Examples of plural apostrophe
Of all the kings’ castles, the Welsh king’s fortress was the most impregnable. (The first half of the sentence demonstrates that there is more than one king with a castle, while the second is only concerned with one king.)
Different types of plural and apostrophes
But there are other versions of the plural in English, both from its Anglo-Saxon roots (words like children, women and geese) and from other languages (words like gateaux, panini or media): what about them?
The fact that no s is involved at the end of the word actually makes it a little simpler, as it means the s can return to its position after the apostrophe without any confusion.
Therefore, we have the geese’s feathers, the panini’s smell or the media’s influence.
But there is a twist in this tale of the apostrophe and its involvement with plural nouns.
The greengrocers’ apostrophe
The stuff of grammarian nightmares, this is the apostrophe that was once used for plurals when the noun ended with a vowel: for example, opera, potato or syringe.
Since the mid-19th century, it has been banished from standard English, but is a habit that dies very hard indeed in popular usage with signs advertising ‘orange’s 80p a kilo’ appearing quite often in markets around the country.
It illustrates nicely the idea that apparently strange punctuation decisions are often borne from older traditions that have perhaps been passed down from one generation to the next without being updated.
Plural abbreviations and numbers
While the general drift of fashion in most areas of apostrophe use is towards more of them, this is one area where they are becoming unpopular.
Abbreviations made up of capital letters (CDs, MPs, BAs or DVDs) no longer have apostrophes, although it was formerly quite common.
Where lower case letters or a mixture of both are involved, then apostrophes are used, according to some authorities. As two examples, I have three PhD’s or There is no i in team, but there are three i’s in individual.
However, for numbers apostrophes are completely out.
The Stone Roses built up a fervent following during the 1980s or The England cricket team managed to score three consecutive 400s.