The apostrophe began life as a device to indicate that part of a word had been left out: ne'er‑do‑well, six o'clock, can't. At a relatively late stage in the history of the English language, the apostrophe became a way of indicating the possessive, showing that something belongs to, or is attached to something (or, more often, someone) else. Some scholars believe that John his book became abbreviated to John's book.
Thus the apostrophe is used to link any two words in a phrase which can be re‑written using of: the book of John = John's book, and the ideas of lecturers = lecturers' ideas. If a phrase can be re‑worded in the "of" form, then the original requires the apostrophe.
While you cannot simply ignore the apostrophe, you should avoid using it where the result would be inelegant. Remember that French, for instance, manages very well just with an "of" form (la plume de ma tante). Many of the examples below are grammatically correct, but they are marked with an asterisk (*) because they are stylistically awful. Try to rewrite any phrase which sounds full of hisses and ZZZZs.
Purists argue that if the apostrophe came to show the possessive through forms like John his book, it should be used only in connection with living creatures, and not with inanimate objects: the man's hat, the cat's whiskers but the engine of the car and the policy of the party.
It is a serious error to insert an apostrophe before the S in the plural of a word. Section 12 deals with the very few exceptions.
Sections 1‑4 deal with the basic rules for the use of the apostrophe.
The rules are simple and university students should be capable of learning them.
1. Most singular nouns form the possessive by adding an: 'S
the boy / the boy's shirt
the girl / the girl's skirt
2. Since the plural of most nouns already ends in S, you simply place the apostrophe after the S:
boys / boys' shoes
girls / girls' handbags
The same applies if the plural is formed by adding ‑ES, or by changing a Y to ‑IES:
the fish's tail/ fishes' tails;
the University's library /
3. A few words form their plural without adding S. To these, simply add apostrophe‑S as if they were singular:
men / men's socks
women / women's liberation
children / children's toys
sheep / sheep's wool
formulae / formulae's complexities*
phenomena / phenomena's appearances*
mice / mice's scrabbling*
4. The apostrophe is not used in possessive pronouns: his, hers, theirs, yours, ours and especially its. It is important to distinguish between its (possessive) and it's ( a contraction of it is):
It's a nice day but The dog ate its bone
Wherever its can be replaced by his, there is no apostrophe.
The same applies to the distinction between whose and who's:
I must find the person whose book this is
I must find the person who's eaten my porridge
ADVANCED APOSTROPHE STUDIES
5. What about words which already end with S, such as James or princess? In Britain, the normal rule is S‑apostrophe‑S:
Keats / Keats's poetry*
the princess / the princess's gown.
However, some favour the simplified usage of adding the apostrophe after the final S, on the same lines as a plural:
the princess' gown.
Common practice in American English is to use S‑apostrophe‑S is for one‑syllable words, but S‑apostrophe only to words with two syllables or more:
Keats / Keats's poetry*
The princess / The princess' gown.
One working rule is: if you say it, write it. The possessive of princess is pronounced princess‑iz, and so deserves S‑apostrophe‑S: princess's.
It is incorrect to place the apostrophe before the final S. The phrase "Keat's poetry" means the poetry of somebody called Keat.
6. With classical or foreign names ending with S, simply add an apostrophe:
However, where the final S is not pronounced, it is usual to add apostrophe‑S:
7. Sometimes a word is omitted from a sentence to avoid an awkward repetition, but an apostrophe may still be necessary to indicate that the omitted word is understood:
Canada's population is five times Scotland's [population]
8. What happens if you have to use the apostrophe in connection with a list of people or things? Suppose you want to indicate that John Major and Tony Blair led rival parties but that both won votes in London, or that Major and Blair adopted an identical stance towards Northern Ireland?
Major's and Blair's parties both won votes in London but
Major and Blair's policy was aimed at peace in Ulster
In both cases, it would be easier to rewrite the sentence to avoid the apostrophe:
The parties led by Major and Blair both won votes in London
The policy of Major and Blair was aimed at peace in Ulster
9. With long and awkward names, the apostrophe is used right at the end: Sir Guy Carleton, later Lord Dorchester's, policy in Canada*; William Drummond of Hawthornden's bequest; Champion the Wonder Horse's television series*.
10. There is no clear rule about the use of the apostrophe in place names, although the trend is towards dropping it altogether, except in a few well‑established traditional examples. St. James's Park in London retains S-apostrophe-S, Newcastle United football club play at St. James' Park [S-apostrophe], while a starkly unpleasant shopping mall in Edinburgh is simply the St. James Centre [no-apostrophe-at-all]. In Canada, the freight rate deal of 1897 is called the Crow's Nest Pass Agreement, but today's maps show the Crowsnest Pass. In some cases, the process has been taken even further. The Hudson's Bay Company was founded in 1670, but today the bay itself is just Hudson Bay.
Generally, the further back in time the individual after whom the place is named, the more likely it is that the apostrophe will have been dropped. It is unlikely that St Andrew will appear to lay claim to St Andrews in Scotland, and it must be a very long time since St Neot visited the towns named after him. (St Mary's in the Scilly Isles preserves the apostrophe because it would look odd for a word to end "ys".)
Occasionally, the apostrophe has a commemorative role. In 1692, insurance brokers decided to transact their business at Edward Lloyd's London coffee house. Lloyd's of London is still a force in the global insurance business, and the apostrophe is a reminder of the fact that Lloyds Bank was an entirely separate business. In 1787, Thomas Lord decided that London needed a major cricket ground. Although it ceased to be a private business in 1860, Lord's preserves its apostrophe to emphasise the fact that cricket is not an aristocratic game.
In Canada, it is still necessary to note each example as it arises. Some well‑known places use the apostrophe: St. John's, Nfld.; Peggy's Cove, NS; Hell's Gate, BC; Queen's Park, Toronto; Barry's Bay, Ont.; St. Ann's, NS. Others have dropped it: St. Catharines, Ont., Smiths Falls, Ont., Rogers Pass, BC. In New Zealand, Hawke's Bay retains its apostrophe at least in official publications.
The apostrophe is still standard in the names of churches and universities: St. Paul's Church, in Halifax, Nova Scotia or Covent Garden, London; Queen's University, in Belfast or Kingston, Ontario. In a famously precise example, Queens' College Cambridge commemorates its foundation by two royal ladies by using the apostrophe to indicate the plural.
Business organisations are increasingly dropping their apostrophes, but individual examples still need to be noted, e.g. Sainbury's Bank, but Barclays.
11. The apostrophe has disappeared from some set phrases, e.g. trades unions, travellers cheques, students union, boys school, Veterans Affairs.
In these cases, the first word has become adjectival [descriptive] rather than possessive: a boys school is a school for boys, but the boys do not actually own it.
Other examples of the adjectival use of nouns include a Commons vote (= a parliamentary vote) and Metis land claims (= Native land claims). However, the apostrophe should be dropped only in well‑established set phrases: travellers cheques but travellers' tickets.
12. CAPITAL LETTERS There is an increasing trend towards the omission of apostrophes where messages are conveyed wholly through the use of capital letters, e.g. in placards and signboards (but not, mercifully, in newspaper headlines). It is a trend that should be resisted.
13. THE APOSTROPHE DOES NOT INDICATE THE PLURAL
A very common error is the insertion of the apostrophe into the plural of a word. There are a few very specific cases where the apostrophe can be used to indicate a plural. These include words which end awkwardly in a vowel, abbreviations and numbers:
My two grandma's
The Medici's of Florence
Scotland had 45 MP's in 1707
Cook hit two 6's
The Depression of the 1930's
There is no reason why the apostrophe cannot be omitted in these examples to avoid confusing lazier minds. There is nothing wrong in grandmas, Medicis, MPs, 6s and 1930s.
Perhaps the only examples in which the apostrophe is really useful are the plurals of lower case [not capital] letters:
dot your i's and cross your t's
mind your p's and q's
there are two m's in accommodation
14. TAILPIECE: THE SILLY APOSTROPHE.
The apostrophe has come to be used in one utterly illogical form, a kind of emphatic double-possessive. Was that your idea? No, it was an idea of Jane's. Strictly speaking, that should be an idea of Jane, but this is a case where the correct form sounds artificial and would never be used. Of course we are all going to continue to talk like that. However, except in quoting direct speech, it is a usage best avoided in writing.