Possessive apostrophe

The possessive ’s, also known as the Saxon genitive or genitive ’s, refers to the use of an apostrophe (which may or may not be followed by the letter "s", depending on the context) to show that the following noun or noun phrase is associated in some way to the preceding noun, e.g. Mary’s house = the house of Mary; goat’s cheese = cheese made from the milk of a goat and Smith’s outstanding lifetime achievements.

While its grammar and pronunciation are intuitive to native English speakers, many students have difficulty in grasping its use and often try to put the definite article in front of proper nouns, etc., as follows:. That said, many native users of English make spelling mistakes, the infamous "greengrocer's apostrophe" (such as ) being a case in point, as is the relatively frequent confusion between it’s and its.

To further complicate matters, some English teachers are guilty of misleading their students into believing that the possessive ’s is only to be used when referring to people, organisations and/or animals. This is simply not so, as the following examples show: a reward for a lifetime’s work and yesterday's weather....

Pronunciation
Main article Pronunciation of the morpheme “-s”

The ending sound of the base word determines the pronunciation of the morpheme “-s”.
 * /s/ for non-sibilant voiceless consonants /f/, /k/, /p/, /t/, and /θ/.
 * Cardiff’s, Mike’s, sheep's, Egypt’s, Elizabeth’s


 * /z/ for vowels and non-sibilant voiced consonants /b/, /d/, /ð/, /g/, /l/, /m/, /n/, /ŋ/, /r/, and /v/.
 * Barbara’s, Bob’s, Maryland’s, Ann’s, Oscar’s


 * /ɪz/ for sibilants: /s/, /z/, /tʃ/, /dʒ/, /ʃ/ and /ʒ/.
 * virus’s, church’s, Marge’s, Bangladesh’s


 * Not pronounced
 * plurals ending in "s": dogs’, friends’
 * classical and biblical names: Augustus’, Jesus’, Moses’

Grammar

 * We use the possessive 's to talk about possession, relationship, physical features, etc. We use it to talk about a noun which “belongs” to a person, a country, organisation, etc.: John’s hair; Anne’s flat; the company's marketing strategy; Spain’s unemployment figures
 * we also use it to talk about something which is used by a person or animal: There are two birds’ nests in that tree; a child’s bicycle;
 * It can also be used for products from living animals: cow’s milk; lamb’s wool;
 * It is often used to say how long things last: three hours’ journey; twenty minutes’ delay;
 * It can indicate the origin of something in a proper name: Murphy's law;

Spelling
Silent possesive is written as a single ’
 * The dogs’ food (the food of the dogs)
 * Jesus’ teachings

Examples
1. singular noun + ’s: Peter’s friends gave him a great present;

2. plural noun + ’: The athletes’ representative negotiated the deal;

3. irregular plural + ’s: The women’s husbands were watching football on TV;

4. We can add ’s or s’ to a whole phrase: Henry the Eighth’s six wives; Anne and John’s house in the country;

While the difference between plural possessives can be shown in written English it can be ambiguous in the spoken language. For example the pronunciation of (2) would be the same if it were:


 * The athlete's representative ...

or


 * The athletes’ representative ...

In practice, however, context usually makes things clear.

Lack of consensus
There's no consensus on how to use it with surnames ending in "s", for example "Davis". By way of example, until its 15th edition (2003), the Chicago Manual of Style recommended Davis', but in its 16th edition (2010), recommends Davis's. On the other hand, Oxford Dictionaries recommends the former.

Writers are recommended to spell as they pronounce. Davids’ is pronounced /ˈdeɪvɪdz/ and Davids’s is pronounced /ˈdeɪvɪdzɪz/.

Titles
Especial care must be taken in the use of the possessive apostrophe in titles. In the same way that we don't say or write, we don't say or write. The correct way is "Shakespeare's Tempest". We can also modify it and say "Shakespeare's last play The Tempest".
 * Homer's Iliad - not: