Nouns: Possessive

Possessive nouns are used to show ownership or possession of something by that noun.

Singular Possessive Nouns

1. To make a singular noun possessive, add an apostrophe and an s.

Dog's collar
(dog+'s)

Bus's engine

(bus+'s)

Charles's sneakers
(Charles+'s)

2. You may sometimes have to show what's called joint possession, which occurs when two or more people own something together. To show joint possession, add an apostrophe and an s to the end of the last noun. 

John and Jennifer's car was stolen. 

Note that if each had a car that was stolen it would be written as such:

John's and Jennifer's car was stolen.

Plural Possessive Nouns

1. To make a plural noun that ends in an s possessive, add an apostrophe (no additional s)

Dogs' collars
(dogs+')

Smiths' house
(Smiths+')

2. To make a plural nouns that doesn't end in s possessive, add an apostrophe and an s.

Children's homework
(children+'s)


Note: Here we used the apostrophe to make a noun possessive but there are other uses such as when forming a contraction.

English Grammar 101: Possessive Nouns
Study.com: What are possessive nouns?