Customer is a different concept from Seller. Dealer is a type of Seller. Dealer is a synonym of Principal. 
Pain can be used for Pleasure. Pleasure is a type of Activity. Activity is related to War. 
Customer <--DistinctFrom--> Seller <--IsA-- Dealer <--Synonym--> Principal 
Pain --UsedFor--> Pleasure --IsA--> Activity <--RelatedTo--> War 