Bill is a synonym of Charge. Overwhelm is a type of Charge. Overwhelming is a form of Overwhelm. 
Department is a type of Sector. Sector is a synonym of Sphere. Sphere is a synonym of Domain. 
Bill <--Synonym--> Charge <--IsA-- Overwhelm <--FormOf-- Overwhelming 
Department --IsA--> Sector <--Synonym--> Sphere <--Synonym--> Domain 