Possessive of nouns. The possessive form of nouns is marked by an apostrophe followed by an -s. After the plural ending ‘s’, however, the possessive -s is omitted:
- the owner’s car
- women’s rights
- footballers’ earnings
- one month’s / four months’ holiday (but a one/four-month stay)
Note that the apostrophe is never used in possessive pronouns:
- its (as distinct from it’s, i.e. ‘it is’), ours, theirs, yours
Nouns ending in -s, including proper names and abbreviations, form their singular possessive with -’s, just like nouns ending in other letters.
- an actress’s pay; Mr Jones’s paper;
- Helios’s future is uncertain; AWACS’s success
The -s after terminal s’ used to be omitted in written English, but this is now done only in classical and biblical names, e.g. Socrates’ philosophy, Xerxes’ fleet.
Note that some place names also omit the apostrophe (Earls Court, Kings Cross). Possessives of proper names in titles (e.g. Chambers Dictionary) sometimes omit the apostrophe as well. There is no apostrophe in Achilles tendon.
Contractions. Apostrophes are also used to indicate contractions, i.e. where one or more letters have been omitted in a word or where two words have been joined together. Contractions are common in informal texts, but not in formal texts. Examples:
- don’t = do not
- it’s = it is (as distinct from the possessive ‘its’)
- who’s = who is (as distinct from whose)
- you’re = you are (as distinct from your)
Plurals of abbreviations. Plurals of abbreviations (MEPs, OCTs, SMEs, UFOs, VDUs) do not take an apostrophe.
Plurals of figures. Plurals of figures do not take an apostrophe:
- Pilots of 747s undergo special training.
Plurals of single letters. The plurals of single lower-case letters may, however, take an apostrophe to avoid misunderstanding:
- Dot your i’s.
- Mind your p’s and q’s.
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