Formation of the possessive case

Singular nouns form their possessive case by adding ‘s to the singular.

• The boy’s dog
• My father’s office

Only the apostrophe (‘) without s is added if the noun contains too many hissing sounds.

• For goodness’ sake
• For conscience’ sake
• For Jesus’ sake
• Moses’ laws

Plural nouns ending in -s form their possessive case by adding only an apostrophe.

• Boys’ school
• Girls’ hostel

Plural nouns that do not end in -s, form the possessive case by adding ‘s.

• Children’s books
• Women’s club

Uses of the possessive case

The possessive case is now used chiefly with the names of living things.

• The lion’s mane
• The minister’s bodyguards
• The King’s palace

The possessive case is not normally used with the names of lifeless things; instead, we use a 

structure with of

• The leg of the table (NOT The table’s leg)
• The cover of the book (NOT The book’s cover)
• The roof of the house (NOT The house’s roof)

Exceptions

The possessive case is often used with the names of personified objects.

• Nature’s laws
• Fortune’s favourites
• At duty’s call
• At wit’s end

The possessive case is also used with nouns denoting time, space and weight.

• In a year’s time
• A day’s work
• At a stone’s throw
• A pound’s weight

The possessive of a proper noun denoting a trade, profession or relationship can often be used to denote a building or place of business.

• She has gone to the baker’s. (= baker’s shop)
• Tonight we are dining at Smith’s (= Smith’s house)