1. When a noun shows ownership or possession
Possessive Nouns
When a noun shows ownership or possession

2. Forming the Possessive of Singular Nouns
To make singular nouns possessive, simply add ‘s

3. Examples the food of the fish = the fish’s food
the claw of the lobster = the lobster’s claw
the book of the boy = the boy’s book
the cheese of the mouse = the mouse’s cheese

4. Singular Possessive: Exception
When a singular noun ends in "s" it may seem the word is plural. However, there are many singular proper nouns that end in "s" like Bess, Jones, etc. When a name ends in "s" or "es", simply add an apostrophe to the end.
the car of Bess = Bess’ car
the house of Jones = Jones’ house

5. Reminder
Singular nouns are made possessive by adding ‘s, unless it is a proper noun that ends in “s” already, like Jones.

6. Forming the Possessives of Plural Nouns
There are 2 ways to make plural nouns possessive…

7. Plural Possessives #1
If the plural noun ends in “s”, simply add an apostrophe to the end
the coats of the girls = the girls’ coats
the marbles of the vases = the vases’ marbles
the cat of the boys = the boys’ cat
Remember: All of the words - girls, vases, and boys - end in “s” and are plural. They only need an apostrophe on the end.

8. Plural Possessives #2 ‘s
If the plural possessive does NOT end in “s” add ‘s

9. Examples the fish of the children = the children’s fish
the babies of the salmon = the salmon’s babies
salmon is plural in this case, but does not end in “s”
the fish of the children = the children’s fish
We know that children is a plural noun, but it does not end in “s.” Therefore, it requires ‘s after the “n”
the boats of the men = the men’s boats

10. Keep in Mind… Singular Possessives
When a singular noun (usually a proper noun like a name) ends in “s”, only add an apostrophe. Otherwise, singular nouns take - ‘s.

11. Plural Possessives
If the plural noun ends in “s”, only add an apostrophe
If the plural noun does not end in “s” (like children, fish, salmon, deer), add -‘s

12. Also Keep In Mind…
Only the noun that possesses or owns something determines the apostrophe or -’s. It does not matter how many things the noun owns or posseses.
Hat example