Grief is the opposite of Joy. Joy is related to Fun. Walking can be used for Fun. 
Balloon is made of Rubber. Rubber is related to Tree. Tree is related to Branch. 
Grief <--Antonym--> Joy <--RelatedTo--> Fun <--UsedFor-- Walking 
Balloon --MadeOf--> Rubber <--RelatedTo--> Tree <--RelatedTo--> Branch 