Curve is the opposite of Line. Line is related to Plot. 
Curve is a type of Magazine. Mandate is a type of Magazine. Mandate is a type of Order. Order is a synonym of Dictate. 
Curve <--Antonym--> Line <--RelatedTo--> Plot 
Curve --IsA--> Magazine <--IsA-- Mandate --IsA--> Order <--Synonym--> Dictate 