Possessive ‘s

Use:

Possessive adjectives after a name and before a noun.
They tell you who owns something.
This is John’s coat. 
Is this Tina’s bag?

Don’t use ‘s after things. 
I clean the garden’s pond every week. =>           I clean the pond in the garden every week.
What’s the book’s name?                           =>           What’s the name of the book? 

You can usually use ‘s after organisations and groups of people.
It’s the government’s decision.   OR          It’s the decision of the government. 
Tom is the company’s new  director.        OR          Tom is the new director of the company.

You can use ‘s after time expressions.
What time is tomorrow’s meeting?
  
You can sometimes use ‘s after countries and cities.
India’s population is rising.
But you cannot do this if it refers to a person.
I met London’s mayor last week.              =>           I met the mayor of London last week.
England’s Queen is well-known. =>           The Queen of England is well-known.

Form:

• To make the possessive form, add ’s to the end of the name.

Is that Jack’s bag?

• With two names, only add ‘s to the second name.

That’s Jane and Harry’s house.                NOT        That’s Jane’s and Harry’s house.

• If something belongs to two or more people, put the apostrophe(‘) after the plural s. Do not write a second s.

My parents’ house is really big. NOT        My parents’s house is really big.

However, if the plural noun is irregular, write the apostrophe (‘) before the S.
The children’s party was great. NOT        The childrens’ party was great.