Extension is derived from Extend. Extend is a synonym of Increase. Expansion is a type of Increase. 
Bag is related to Property. Property is related to Let. Let is related to English. English is related to British. 
Extension --DerivedFrom--> Extend <--Synonym--> Increase <--IsA-- Expansion 
Bag <--RelatedTo--> Property <--RelatedTo--> Let <--RelatedTo--> English <--RelatedTo--> British 